Gitaly has changed semantics of the RemoveRepository RPC call to return
an error in case the repository that is about to be deleted doesn't
exist anymore in commit f328e3f70 (repository: Implement atomic locking
semantics for RemoveRepository, 2021-11-30). This change was required
such that Gitaly can provide proper locking semantics for repositories,
but it has broken expectations on our side that removing a nonexisting
repository is an idempotent action.

Adapt to the semantic change by rescuing from `NoRepository` errors in
`Repository#remove`.