The VerticalPodAutoscaler rollout pulls registry.k8s.io/autoscaling/vpa-recommender.
Serve it through the existing k8s-registry pull-through cache, consistent with how
external-dns and sig-storage images from registry.k8s.io are already gated.
The grafana-operator creates Grafana pods from docker.io/grafana/grafana,
which the dockerhub remote did not allow, so the pods would ImagePullBackOff.
Add the ^grafana/ pattern so the grafana image (and image-renderer) proxy
through artifactapi.