Revisit 40% threshold on CPU load for quay.io pods

Currently we are alerting whenever a quay.io Pod uses more than 40% of its CPU limit (13) for more than 5 minutes.  Spot checking the cluster, most Pods are under 5 cores, but a few are between 5 and 6 (which seems normal).

Suggest that we increase the alert threshold to 50% (6.5 cores) to reduce alerts flapping.

https://gitlab.cee.redhat.com/service/app-interface/blob/master/resources/quay-p/quay/quay.alerts.prometheusrules.yaml