Revert "Merge branch 'update-ref-to-8.15.0' into 'master'"

This reverts merge request !234 (merged)

Related incident: gitlab-com/gl-infra/production#18126 (closed)

Smoke tests in gstg-cny are failing due to the runners being unable to pull the image, e.g.: https://ops.gitlab.net/gitlab-org/quality/staging/-/jobs/14211578

 ERROR: Job failed: failed to pull image "registry.ops.gitlab.net/gitlab-org/gitlab-build-images/debian-bookworm-ruby-3.1.5:bundler-2.5-docker-24.0.5" with specified policies [always]: Error response from daemon: manifest for registry.ops.gitlab.net/gitlab-org/gitlab-build-images/debian-bookworm-ruby-3.1.5:bundler-2.5-docker-24.0.5 not found: manifest unknown: manifest unknown (manager.go:250:0s)

Previously passed smoke test was using a different image:

Using Docker executor with image registry.ops.gitlab.net/gitlab-org/gitlab-build-images/debian-bullseye-ruby-3.0:bundler-2.3-docker-23.0.1

and the debian-bookworm image doesn't seem to exist, as suggested by that error message https://ops.gitlab.net/gitlab-org/gitlab-build-images/container_registry?orderBy=UPDATED&sort=desc&search[]=bookworm

For some reason, the image didn't land in ops gitlab-build-images container registry.

To unblock deployments, we should revert and continue investigation on why the image isn't there.