Make gitlab-kas deployment not depend on gitlab.com

During the PG12 upgrade maintenance we noticed that gitlab-kas pods couldn't be scaled up again while gitlab.com was still down, as it is trying to pull images from registry.gitlab.com (which is depending on API for logins).

We should change this to make it get the images from dev.gitlab.org as we do for our other deployments to avoid deadlocks during deployments.

Failed to pull image "registry.gitlab.com/gitlab-org/cluster-integration/gitlab-agent/kas:v13.10.1": rpc error: code = Unknown desc = Error response from daemon: received unexpected HTTP status: 503 Service Unavailable

/cc @ggillies