Updating cluster-monitoring-operator-container image to be consistent with ART for 4.21

Reconciling with https://github.com/openshift/ocp-build-data/tree/5c68d71385f72cd67a199bc4590068053a833c7d/images/cluster-monitoring-operator.yml

Author: AOS Automation Release Team

.ci-operator.yaml

@@ -1,4 +1,4 @@
 build_root_image:
   name: release
   namespace: openshift
-  tag: rhel-9-release-golang-1.24-openshift-4.20
+  tag: rhel-9-release-golang-1.24-openshift-4.21

Dockerfile

@@ -1,12 +1,12 @@
 # When bumping the Go version, don't forget to update the configuration of the
 # CI jobs in openshift/release.
-FROM registry.ci.openshift.org/ocp/builder:rhel-9-golang-1.24-openshift-4.20 AS builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-9-golang-1.24-openshift-4.21 AS builder
 WORKDIR /go/src/github.com/openshift/cluster-monitoring-operator
 COPY . .
 ENV GOFLAGS="-mod=vendor"
 RUN make operator-no-deps && make tests-ext-build && gzip tests-ext
 
-FROM registry.ci.openshift.org/ocp/4.20:base-rhel9
+FROM registry.ci.openshift.org/ocp/4.21:base-rhel9
 LABEL io.k8s.display-name="OpenShift cluster-monitoring-operator" \
       io.k8s.description="This is a component of OpenShift and manages the lifecycle of the Prometheus based cluster monitoring stack." \
       io.openshift.tags="openshift" \