Fetch the proper mailroom version from GitLab for 12.9
- mailroom was forked to a new gem for 12.9
See CNG MR here: gitlab-org/build/CNG!393 (merged)
And upstream MR here: gitlab-org/gitlab!25869 (merged)
See CNG MR here: gitlab-org/build/CNG!393 (merged)
And upstream MR here: gitlab-org/gitlab!25869 (merged)