Update main docs based on markdownlint errors (3/3)

If we want to turn on markdownlint linting in this project, we'll have to clear out the errors it found first.

This MR addresses all the docs in doc/developer:

git-over-ssh.md:1:15 MD044/proper-names Proper names should have the correct capitalization [Expected: Git; Actual: git]
git-over-ssh.md:3:74 MD044/proper-names Proper names should have the correct capitalization [Expected: Git; Actual: git]
git-over-ssh.md:13:18 MD044/proper-names Proper names should have the correct capitalization [Expected: Git; Actual: git]
git-over-ssh.md:20:20 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
git-over-ssh.md:24:24 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
git-over-ssh.md:28:6 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
git-over-ssh.md:30:50 MD044/proper-names Proper names should have the correct capitalization [Expected: NGINX Ingress; Actual: NGINX ingress]
git-over-ssh.md:51:117 MD044/proper-names Proper names should have the correct capitalization [Expected: Git; Actual: git]
git-over-ssh.md:55:47 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
git-over-ssh.md:57:25 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
git-over-ssh.md:59:26 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
gitlab-upgrades.md:8 MD032/blanks-around-lists Lists should be surrounded by blank lines [Context: "- If these versions match, the..."]
gitlab-upgrades.md:51 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
gitlab-upgrades.md:52:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl -n gitlab-system app..."]
gitlab-upgrades.md:57:3 MD044/proper-names Proper names should have the correct capitalization [Expected: GitLab; Actual: gitlab]
gitlab-upgrades.md:63 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
installation.md:3:43 MD044/proper-names Proper names should have the correct capitalization [Expected: GitLab Operator; Actual: GitLab operator]
installation.md:10:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 2; Style: 1/1/1]
installation.md:14:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 3; Style: 1/1/1]
installation.md:28:4 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
installation.md:32:34 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
installation.md:62 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "    ```"]
installation.md:63:5 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ GL_OPERATOR_VERSION=0.1.0"]
installation.md:64:5 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ PLATFORM=kubernetes # or "op..."]
installation.md:65:5 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl create namespace git..."]
installation.md:66:5 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl apply -f https://git..."]
installation.md:80:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 2; Style: 1/1/1]
installation.md:107:1 MD029/ol-prefix Ordered list item prefix [Expected: 1; Actual: 3; Style: 1/1/1]
installation.md:109 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "   ```"]
installation.md:110:4 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl -n gitlab-system app..."]
installation.md:115 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "   ```"]
installation.md:116:4 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$  kubectl -n gitlab-system lo..."]
installation.md:121 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "   ```"]
installation.md:140 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
installation.md:141:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl -n gitlab-system del..."]
installation.md:148 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
installation.md:149:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ GL_OPERATOR_VERSION=0.1.0"]
installation.md:150:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ PLATFORM=kubernetes # or "op..."]
installation.md:151:1 MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ kubectl delete -f https://gi..."]
known-limitations.md:1 MD002/first-heading-h1/first-header-h1 First heading should be a top-level heading [Expected: h1; Actual: h2]
openshift-cluster-setup.md:19:50 MD034/no-bare-urls Bare URL used [Context: "https://cloud.redhat.com/opens..."]
openshift-cluster-setup.md:34:71 MD034/no-bare-urls Bare URL used [Context: "https://cloud.redhat.com/opens..."]
openshift-cluster-setup.md:46:87 MD044/proper-names Proper names should have the correct capitalization [Expected: JSON; Actual: json]
openshift-cluster-setup.md:50:57 MD044/proper-names Proper names should have the correct capitalization [Expected: SSH; Actual: ssh]
openshift-cluster-setup.md:68:87 MD044/proper-names Proper names should have the correct capitalization [Expected: JSON; Actual: json]
openshift-cluster-setup.md:75:78 MD044/proper-names Proper names should have the correct capitalization [Expected: GitLab Operator; Actual: GitLab operator]
openshift-cluster-setup.md:79:33 MD034/no-bare-urls Bare URL used [Context: "https://github.com/openshift/i..."]
openshift-cluster-setup.md:80:16 MD034/no-bare-urls Bare URL used [Context: "https://github.com/openshift/o..."]
openshift-cluster-setup.md:81:44 MD034/no-bare-urls Bare URL used [Context: "https://mirror.openshift.com/p..."]
openshift-cluster-setup.md:82:56 MD034/no-bare-urls Bare URL used [Context: "https://access.redhat.com/docu..."]
openshift-cluster-setup.md:83:23 MD034/no-bare-urls Bare URL used [Context: "https://docs.openshift.com/con..."]
openshift-cluster-setup.md:84:36 MD034/no-bare-urls Bare URL used [Context: "https://docs.openshift.com/con..."]
operator-upgrades.md:24 MD040/fenced-code-language Fenced code blocks should have a language specified [Context: "```"]
security-context-constraints.md:8:152 MD044/proper-names Proper names should have the correct capitalization [Expected: OpenShift; Actual: Openshift]
security-context-constraints.md:55:9 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
security-context-constraints.md:56:15 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
security-context-constraints.md:58:29 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
troubleshooting.md:4:25 MD044/proper-names Proper names should have the correct capitalization [Expected: GitLab Operator; Actual: GitLab operator]
troubleshooting.md:52:1 MD004/ul-style Unordered list style [Expected: dash; Actual: asterisk]
troubleshooting.md:53:1 MD004/ul-style Unordered list style [Expected: dash; Actual: asterisk]
troubleshooting.md:54:1 MD004/ul-style Unordered list style [Expected: dash; Actual: asterisk]
troubleshooting.md:55:1 MD004/ul-style Unordered list style [Expected: dash; Actual: asterisk]
troubleshooting.md:59:5 MD044/proper-names Proper names should have the correct capitalization [Expected: GitLab Operator; Actual: GitLab operator]
troubleshooting.md:98:1 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
troubleshooting.md:99:1 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]
troubleshooting.md:114:33 MD044/proper-names Proper names should have the correct capitalization [Expected: NGINX Ingress; Actual: NGINX ingress]
troubleshooting.md:119:50 MD044/proper-names Proper names should have the correct capitalization [Expected: Ingress; Actual: ingress]

Related to #363 (closed)