Update names of many Git navigation entries

What does this MR do and why?

For gitlab#468098 (closed), begin the process of refactoring the navigation items.

Screenshots, screen recordings, or links to review app

• Before: https://docs.gitlab.com/ee/topics/git/
• After: https://eread-update-names-of-many-git-navigation-entries.docs.gitlab-review.app/ee/topics/git/

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.