Use qa images from registry.gitlab.com registry rather than docker hub
Currently the qa images are being pulled from Docker Hub for following reason
- Test the image the the customers will be using
- There was a requirement to test nightly images that go to Docker Hub but not anymore
- ??
This needs to be changed to use registry.gitlab.com
for the following reasons
- Reasons mentioned https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/7459
- Reduce dependency
- The requirement to test nightly images from Docker Hub isn't there anymore.(Need confirmation)