praefect: Revert relative path rewriting in RepositoryReplicas

With 8d3767c7 (Rewrite relative path in RepositoryReplicas, 2022-03-02) we have introduced rewriting of the repository's relative path for the RepositoryReplicas RPC. This has introduced new usage of the repository store into the code path, which is required such that we can obtain the replica path from the database. Unfortunately, this is causing failures downstream in Rails, which is still not using a database and thus uses a stubbed-out repository store.

Fixing this isn't quite trivial because we can't create a simple stub implementation of GetReplicaPath(). We'd have two choices: either return successfully with a bogus replica path, or return an error like ErrRepositoryNotFound, and neither of those options fixes the failure observed in Rails.

Revert the commit for now. We're actively working to migrate Rails to use a database for its tests, so the limitations we have will go away. Furthermore, the actual path rewriting is blocked by the very same migration, so the revert shouldn't block any ongoing work either.