Upgrade GitLab QA image to Ruby 2.5
Upgrade GitLab QA image to Ruby 2.5

GitLab is now shipping with Ruby 2.5.3, so we should make the
version consistent for the QA image as well.

stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,dreampet/gitlab,axilleas/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,mmkassem/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,iiet/iiet-git