Revert "Remove yaml_safe_load_file patch", re-introducing Ruby 2.7 support
We tried to roll out the latest version of gitlab-exporter, but ran into issues on our redis fleet: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/4053. On redis we pin an older omnibus version, and thus we also ship with an older redis version.
In order to unblock other critical fixes to gitlab-exporter https://gitlab.com/gitlab-org/gitlab-exporter/-/merge_requests/193, it is probably easiest to re-introduce Ruby 2.7 support for now.
Once omnibus has been bumped on the entire redis fleet, we can then properly deprecate Ruby 2.7.
This reverts merge request !192 (merged).