Fix YAML warnings on removals files

What does this MR do?

Fixes most of the YAML warnings spotted in https://gitlab.com/gitlab-org/gitlab/-/jobs/4270600305 that made it harder to see the actual error.

$ yamllint -d "{extends: default, rules: {line-length: disable, document-start: disable}}" $LINT_PATHS
.gitlab/ci/preflight.gitlab-ci.yml
  37:16     warning  too few spaces before comment  (comments)
.gitlab/ci/package-and-test-nightly/main.gitlab-ci.yml
  30:20     warning  too few spaces before comment  (comments)
.gitlab/ci/review-apps/main.gitlab-ci.yml
  95:12     warning  too few spaces before comment  (comments)
data/deprecations/16-0-deprecate-postgresql-13.yml
  22:29     error    too many spaces after colon  (colons)
data/removals/16_0/16-0-dast-api-variable-removal.yml
  7:67      warning  too few spaces before comment  (comments)
data/removals/16_0/16.0-config-fields-runner-helm-chart.yml
  7:67      warning  too few spaces before comment  (comments)
data/removals/16_0/16-0-grafana-chart.yml
  18:10     warning  too few spaces before comment  (comments)
data/removals/16_0/16.0-eol-windows-server-2004-and-20H2.yml
  7:73      warning  too few spaces before comment  (comments)
data/removals/16_0/16-0-postgresql-12.yml
  16:10     warning  too few spaces before comment  (comments)
data/removals/16_0/16.0-runner-api-does-not-return-paused-active.yml
  7:67      warning  too few spaces before comment  (comments)
data/removals/16_0/16-0-limit-ci-job-token.yml
  5:23      warning  too few spaces before comment  (comments)
Cleaning up project directory and file based variables
00:01
ERROR: Job failed: exit code 1

Related issues

Created as part of work for Add support for PostgreSQL 14 (&9065 - closed) but is not actually related to it in any way.

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• If you're adding or changing the main heading of the page (H1), ensure that the product tier badge is added.
• If you are a GitLab team member, request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

If you aren't sure which tech writer to ask, use roulette or ask in the #docs Slack channel.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • Ensure a release milestone is set.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the reviews above. Maintainer's review can occur before or after a technical writer review.