Unmark Gitaly features as OPT_OUT until the gRPC proxy issue is fixed

What does this MR do?

Unmark Gitaly features as OPT_OUT until the gRPC proxy issue is fixed

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

No

Why was this MR needed?

gRPC has a bug that causes it to ignore no_proxy settings. So gitaly calls don't work for uses with proxy. We can't mark features as OPT_OUT until this issue is solved.

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

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/38333