CNG: merges to stable not properly accounting for CE/EE
An MR directly to a stable branch can't follow the logic related to stable branches and the handling of CE vs EE variants.
gitlab-rails-ee was attempting to pull the CE tag of it's own assets image.
Steps to reproduce
EE images sometimes try to use CE assets
EE images always properly use EE assets.
Error response from daemon: manifest for registry.gitlab.com/gitlab-org/gitlab/gitlab-assets-ee:v13.1.0 not found: manifest unknown: manifest unknown