Rename cluster_metrics_new.yml

Summary

Once !15709 (merged) is merged, we will want to go back and rename https://gitlab.com/gitlab-org/gitlab-ee/blob/d6944667bde75e81a1d10945c7645b134a447b05/ee/config/prometheus/cluster_metrics_new.yml so it doesn't have _new in it's name and update all references.