Stop publishing helper image to DockerHub
Overview
With !2540 (merged) and !2554 (merged) we started publish the helper image to DockerHub and in #27218 (closed) it pulls the helper image from registry.gitlab.com
by default. We should have 1 single source of truth of where our helper image lives for maintainability perspective and reduce the dependencies we have on 3rd party services that we don't have control over.