Remove Gitlab::RepoPath.strip_storage_path

What does this MR do?

This used to be executed because of the post receive worker, but this uses Gitlab::GlRepository.parse now. So this removes dead code and reduces the number of calls on #legacy_storage_path.

My assumptions are based on the constraints set in config/routes/git_http.rb

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
• [-] End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

None, found scanning for DEPRECATION WARNING in our logs.