Docs: Update omnibus-gitlab doc links (batch 1)

What does this MR do?

In response to the Hugo migration, updates links in gitlab-org/omnibus-gitlab to point to the new documentation site:

• Does not use /ee
• Uses / instead of .html
• Uses / instead of index.html

Updating links in batches. This is batch one.

Note: Some of the origin links were broken. I replaced all dead links with my best effort guess. For example, I changed

https://docs.gitlab.com/ee/development/documentation/#move-or-rename-a-page =>

https://docs.gitlab.com/development/documentation/redirects/

Related issues

Contractor: Update links to the new docs site a... (gitlab-org/technical-writing/docs-gitlab-com#271 - moved)

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• When ready for review, MR is labeled workflowready for review per the Distribution MR workflow

If you are only adding documentation, do not add any of the following labels:

• ~"feature"
• ~"frontend"
• ~"backend"
• ~"bug"
• ~"database"

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

Review 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 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.
  • 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 above reviews. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.