Allow differing relative paths in ReplicateRepository

ReplicateRepository checks that the relative paths of the source and
the target repositories are the same. This is more of a sanity check
than a requirement. With Prafect rewriting relative paths, this check
fails and causes ReplicateRepository to fail with Praefect in front.
Previously the tests were not running with Praefect enabled which
allowed for this regression to slip through. This commit removes the
check which allows the RPC to work with Praefect enabled. The target
repository has a rewritten relative path as it's where the Gitaly will
store the replicated repository. The source repository's path is not
rewritten by Praefect as Gitaly fetches it by going through the source
storage. If the source storage is hosted by a Praefect, the relative
path would be rewritten at that point by Praefect.

Changelog: fixed