Check if new DockerHub pricing will affect CI Runners
### Overview
DockerHub has announced new pricing plans https://hub.docker.com/pricing the most worrying one that will effect us is:
> Data transfer (per 6 hours)
>
> Anonymous users 100 pulls
>
> Authenticated users (Docker ID) 200 pulls
If I understand this correctly this would be that when our shared runners on GitLab.com will try an pull images and the user didn't specify any `DOCKER_AUTH_CONFIG` it will fall under the `Anonymous users` and we might end up being rate limited.
We have [DockerHub mirroring in place](https://cloud.google.com/container-registry/docs/pulling-cached-images) which also helps with this because we don't end up relying on DockerHub that much since most images are available in the mirror.
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