Enable merged results pipeline in Canonical and Security mirror
With !6296 (merged), pipelines on omnibus-gitlab
no longer depends on omnibus-gitlab-mirror
. One thing this lets us do is use merged result pipelines for MRs. This is preferred for development so that the built results will match the statue of the target branch.
This will also let omnibus-gitlab security MRs to be early merged, like other components. (Reference: release-tools!1955 (merged), release-tools!1218 (merged), gitlab-com/gl-infra/delivery#1244 (closed), and gitlab-com/gl-infra/delivery#1122 (closed))