Merged the 'groups' and 'projects' tabs when viewing user profiles

What does this MR do?

As mentioned in #24752 (closed), this MR removes the 'Groups' tab when viewing a user profile in the admin section, and moves the functionality into the 'Projects' tab.

Are there points in the code the reviewer needs to double check?

Whether the tab title is appropriate.

Why was this MR needed?

The 'Projects' tab replicates most of the functionality in the 'Groups' tab, so it made sense to merge them into one tab.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

#24752 (closed)