Don't pass the repository path to Gitlab Shell

All Git SSH commands supported by Gitlab-shell use Gitaly now. However, we still pass back the full repository path from gitlab-rails to gitlab-shell when gitlab-shell validates a Git SSH command on the internal API. This is a problem because gitlab-rails cannot know the path to the repository in the Gitaly world.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Surfaced because of gitaly#1139 (closed)