Merge branch 'trigger-jobs-in-sec-mirror' into 'master'

Enable Trigger:(ce|ee)-package jobs in security MR pipelines

See merge request gitlab-org/omnibus-gitlab!4595

gitlab-ci-config/gitlab-com.yml

@@ -89,6 +89,7 @@
     - bundle exec rake build:trigger
   only:
     - branches@gitlab-org/omnibus-gitlab
+    - branches@gitlab-org/security/omnibus-gitlab
   except:
     refs:
       - triggers