Docker rate limits causing flaky CI

[corneliusroemer]

We sometimes get failures of integration tests because docker tells us 429 too many requests.

We might want to ban docker as a container registry - replace with others that aren't as annoying.

In this case we hit postgres pull limits.

Main Loculus DB pod loculus-database-86db87c5cc-lf2fm is Pending with ImagePullBackOff, and events show: 429 Too Many Requests ... You have reached your unauthenticated pull rate limit while pulling docker.io/library/postgres:15.12. 

Keycloak DB pod loculus-keycloak-database-7557ffcd59-28d4p is also Pending with the same ImagePullBackOff / 429 Too Many Requests.