Error removing wiki repo when deleting user

We need to check for repo existence first

https://sentry.gitlab.net/gitlab/gitlabcom/issues/1745571/?referrer=gitlab_plugin

GRPC::NotFound: 5:GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git". debug_error_string:{"created":"@1596981722.980664863","description":"Error received from peer ipv4:10.221.2.153:9999","file":"src/core/lib/surface/call.cc","file_line":1055,"grpc_message":"GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git"","grpc_status":5}
  grpc/generic/active_call.rb:29:in `check_status'
    fail GRPC::BadStatus.new_status_exception(
  grpc/generic/active_call.rb:180:in `attach_status_results_and_complete_call'
    recv_status_batch_result.check_status
  grpc/generic/active_call.rb:376:in `request_response'
    attach_status_results_and_complete_call(batch_result)
  grpc/generic/client_stub.rb:178:in `block in request_response'
    c.request_response(req, metadata: metadata)
  grpc/generic/interceptors.rb:170:in `intercept!'
    return yield if @interceptors.none?
...
(126 additional frame(s) were not displayed)

Gitlab::Git::Repository::NoRepository: 5:GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git". debug_error_string:{"created":"@1596981722.980664863","description":"Error received from peer ipv4:10.221.2.153:9999","file":"src/core/lib/surface/call.cc","file_line":1055,"grpc_message":"GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git"","grpc_status":5}
  gitlab/git/wraps_gitaly_errors.rb:9:in `rescue in wrapped_gitaly_errors'
    raise Gitlab::Git::Repository::NoRepository.new(e)
  gitlab/git/wraps_gitaly_errors.rb:6:in `wrapped_gitaly_errors'
    def wrapped_gitaly_errors(&block)
  gitlab/git/repository.rb:144:in `rename'
    wrapped_gitaly_errors do
  gitlab/shell.rb:92:in `mv_repository'
    Gitlab::Git::Repository.new(storage, "#{disk_path}.git", nil, nil).rename("#{new_disk_path}.git")
  gitlab/metrics/instrumentation.rb:161:in `block in mv_repository'
    .measure { super }
...
(113 additional frame(s) were not displayed)

Gitlab::Git::Repository::NoRepository: 5:GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git". debug_error_string:{"created":"@1596981722.980664863","description":"Error received from peer ipv4:10.221.2.153:9999","file":"src/core/lib/surface/call.cc","file_line":1055,"grpc_message":"GetRepoPath: not a git repository: "/var/opt/gitlab/git-data/repositories/@hashed/9b/ae/9bae2b0778b10136f271199b671d79c9113c4063e1c0048fcd9f4d34d5c3f16e.wiki.git"","grpc_status":5}