Projects::CommitsController#signatures - GRPC::DeadlineExceeded: 4:Deadline Exceeded

https://sentry.gitlab.net/gitlab/gitlabcom/issues/615647/

GRPC::DeadlineExceeded: 4:Deadline Exceeded
  grpc/generic/active_call.rb:31:in `check_status'
    fail GRPC::BadStatus.new_status_exception(
  grpc/generic/active_call.rb:181:in `attach_status_results_and_complete_call'
    recv_status_batch_result.check_status
  grpc/generic/active_call.rb:170:in `receive_and_check_status'
    attach_status_results_and_complete_call(batch_result)
  grpc/generic/active_call.rb:338:in `each_remote_read_then_finish'
    receive_and_check_status
  gitlab/gitaly_client/commit_service.rb:383:in `each'
    response.each do |message|
...
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GRPC::DeadlineExceeded: 4:Deadline Exceeded