Fix LDAP group sync permission override UI

What does this MR do?

• Enables the permission controls for overridden member permissions

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

Please make sure that I have properly captured our original intent here.

E.g. What happens when expiration date passes on an overridden perm? Do we revert them? Should the expiration date be disabled if the group has LDAP group sync? In the 3rd screenshot of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/822, the expiration date textbox is enabled after override. I'm just not sure about this one.

Edit: Answered myself here https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5003#note_64000266

Why was this MR needed?

https://gitlab.com/gitlab-org/gitlab-ee/issues/5301

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/5301