pgbouncer: Use new bitnamilegacy container registry
Bitnami has deprecated some images, including pgbouncer.
They moved it to a new container registry, called bitnamilegacy, and is no longer updated.
We might need to move to a supported image some time but for now, to unblock failing pipelines, let's just use the same image as before, wihch was moved to docker.io/bitnamilegacy/pgbouncer
See here: