Fix AuthorizationPolicy Labels for Prometheus

Labels updated from app to app.kubernetes.io/name=prometheus so the matchLabels need to be updated as well.

With istio.hardened.enabled to true the url for prometheus is giving a RBAC: access denied until fixed.

Update: After a team war room where the team looked further, the mismatch label was caused by this kiali MR in Big Bang repo with this MR merging a fix for this mismatch label.