Deadline exceeded in filter_shas_with_signatures

https://sentry.gitlab.net/gitlab/gitlabcom/issues/971445/

GRPC::DeadlineExceeded: 4:Deadline Exceeded
  grpc/generic/active_call.rb:31:in `check_status'
    fail GRPC::BadStatus.new_status_exception(
  grpc/generic/bidi_call.rb:209:in `block in read_loop'
    batch_result.check_status
  grpc/generic/bidi_call.rb:195:in `loop'
    loop do
  grpc/generic/bidi_call.rb:195:in `read_loop'
    loop do
  gitlab/gitaly_client/commit_service.rb:358:in `each'
    response.flat_map do |msg|
...
(87 additional frame(s) were not displayed)

4:Deadline Exceeded