Decommission `gitlab-operator-v127` GKE cluster

Summary

Summary

It is time to remove the gitlab-operator-v127 GKE cluster.

Maintenance support ended 2024-06-28 for Kubernetes 1.27, https://endoflife.date/kubernetes.

Steps:

• remove CI jobs for 127 cluster Drop Kubernetes 1.27 and 1.28 CI testing (!1014 - merged) • Clemens Beck • 17.6
• move vcluster CI jobs to newest cluster in CI config
• remove CI variables and 1Password items for 125 cluster
• delete the 127 cluster itself

1.27 has not yet been deprecated in installation table docs: https://gitlab.com/gitlab-org/cloud-native/gitlab-operator/-/blob/master/doc/installation.md?ref_type=heads#cluster. We should deprecate in docs before removing support.

1.27 cluster lifecycle issue: https://gitlab.com/gitlab-org/distribution/infrastructure/kubernetes-provisioning/-/issues/48+