Starting October 10, 2023, mirror.gcr.io is transitioning to being hosted on Artifact Registry

## Change Starting October 10, 2023, `mirror.gcr.io` is transitioning to being hosted on Artifact Registry. This change is taking place on a region by region basis, and doesn't require you to change your usage of `mirror.gcr.io` unless you are using it within a VPC service perimeter. For information on how to use `mirror.gcr.io` in a VPC service perimeter after the transition to being hosted on Artifact Registry, see [Using Artifact Registry with VPC Service Controls](https://cloud.google.com/artifact-registry/docs/securing-with-vpc-sc#ar-vpc).