Description of problem:
In KAS-O logs, below event is high-frequency looped:
2021-05-06T07:09:03.614448160Z I0506 07:09:03.614391       1 event.go:282] Event(v1.ObjectReference{Kind:"Deployment", Namespace:"openshift-kube-apiserver-operator", Name:"kube-apiserver-operator", UID:"54086850-4a33-4773-96c1-6828b83ba46e", APIVersion:"apps/v1", ResourceVersion:"", FieldPath:""}): type: 'Normal' reason: 'PrometheusRuleUpdated' Updated PrometheusRule.monitoring.coreos.com/v1 because it changed
...<snipped another 12 same events before next second 2021-05-06T07:10>...

Version-Release number of selected component (if applicable):
4.8.0-0.nightly-2021-05-06-003426

How reproducible:
Always

Steps to Reproduce:
1. Check KAS-O logs

Actual results:
1. Above log is high-frequency looped.
$ grep 'Updated PrometheusRule.monitoring.coreos.com/v1 because it changed' kas-o.log | wc -l                                                                                             
3033

Then changed operatorLogLevel to Debug:
$ oc edit kubeapiserver cluster
...
  operatorLogLevel: Debug
...

Checked KAS-O logs again, found:
2021-05-06T07:48:03.481235292Z I0506 07:48:03.481184       1 monitoring.go:122] PrometheusRule "openshift-kube-apiserver/cpu-utilization" changes: {}
2021-05-06T07:48:03.490663221Z I0506 07:48:03.490596       1 event.go:282] Event(v1.ObjectReference{Kind:"Deployment", Namespace:"openshift-kube-apiserver-operator", Name:"kube-apiserver-operator", UID:"54086850-4a33-4773-96c1-6828b83ba46e", APIVersion:"apps/v1", ResourceVersion:"", FieldPath:""}): type: 'Normal' reason: 'PrometheusRuleUpdated' Updated PrometheusRule.monitoring.coreos.com/v1 because it changed

Each event is preceded by `"openshift-kube-apiserver/cpu-utilization" changes: {}`. That is, actual change is always empty {}, i.e. actually no change at all.

Double checked `oc get PrometheusRule cpu-utilization -n openshift-kube-apiserver --watch`, the output shows one item, then never has new output, i.e. actually no change either.

Repeating `oc get PrometheusRule cpu-utilization -o yaml`, the output never "changes" either between repeated executions.

Expected results:
1. No loop, given cpu-utilization actually has no any "changes".

Additional info:
Related bug: bug 1951705. Seems introduced by that bug.