Update pages affected by UI change

What does this MR do?

The work being done in Create a top-level Merge Request section under ... (#119451 - closed) to move the merge request administrative settings from Settings > General to Settings > Merge Requests requires changes to multiple changes in the UI. Right now, I'm not sure how many of these settings are actually moving (I couldn't tell from the screenshot) so I've edited every instance I could find. I'll assign it over to Phil and Annabel to figure out which ones are accurate. I'm trying to hold to our stance of "first draft should come from Engineering," as I have a limited amount of time I can spend on original research into changes.

Phil, could you please set a dependency on this MR so it doesn't merge too soon?

Related issues

Related to Create a top-level Merge Request section under ... (#119451 - 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 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.