CTRT edits to Code Owners doc

What does this MR do?

MR no. 1 of several

Edit https://docs.gitlab.com/ee/user/project/codeowners/ to follow the CTRT content format.

Review app:

• Make sure the page follows the CTRT topic types.
  • You might need to combine topics or re-order content. You can open as many MRs as you'd like/you need.
• When working on the concept section of your page, pay special attention to the What and Why of the feature. If this information is missing, work with an SME to add it.
• Review the search terms for the page: https://search.google.com/u/1/search-console/performance/search-analytics?resource_id=https://docs.gitlab.com/&breakdown=query&page=!https://docs.gitlab.com/ee/user/project/codeowners/
• Ensure any notes or warnings on the page are absolutely necessary.
• Pay attention to the right nav. When you're done with the full page, it should be easy to scan. If you open multiple MRs over time, this can be a final step.

Assign your MR to Fiona for review.

Related issues

Part of FY24Q3 TW OKR: Refactor high visibility pages f... (technical-writing#839 - closed)

This MR addresses:

• Make it clear that "no section" in Codeowners i... (#396301 - closed)
• CODEOWNERS - Default always gets applied in add... (#296869 - closed)

Future MRs might address:

• Improve Codeowner docs: require approval from m... (#386006)
• CODEOWNERS does not work when namespace path ch... (#356123)
• Docs feedback: subgroup membership impact (#327479 - closed)

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.