Upgrade to Ruby 2.5.3
We found in CE that the main difference in behavior is with URI.join
(https://gitlab.com/gitlab-org/gitlab-ce/issues/53180). No instances in gitaly-ruby were found of this call.
Ruby 2.5.x claims to be 5-10% faster than Ruby 2.4.x, so let's use it.
Edited by GitLab Release Tools Bot