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

Reconciling with https://github.com/openshift/ocp-build-data/tree/4fbe3fab45239dc4be6f5d9d98a0bf36e0274ec9/images/monitoring-plugin.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.art

@@ -1,4 +1,4 @@
-FROM registry.ci.openshift.org/ocp/builder:rhel-9-base-nodejs-openshift-4.20 AS web-builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-9-base-nodejs-openshift-4.21 AS web-builder
 
 # Copy app sources
 COPY $REMOTE_SOURCES $REMOTE_SOURCES_DIR
@@ -17,7 +17,7 @@ RUN test -d ${REMOTE_SOURCES_DIR}/cachito-gomod-with-deps || exit 1; \
  && make build-frontend
 
 
-FROM registry.ci.openshift.org/ocp/builder:rhel-9-golang-1.24-openshift-4.20 AS go-builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-9-golang-1.24-openshift-4.21 AS go-builder
 
 COPY $REMOTE_SOURCES $REMOTE_SOURCES_DIR
 WORKDIR $REMOTE_SOURCES_DIR/cachito-gomod-with-deps/app
@@ -28,7 +28,7 @@ ENV CGO_ENABLED=1
 RUN source $REMOTE_SOURCES_DIR/cachito-gomod-with-deps/cachito.env \
   && make build-backend BUILD_OPTS="-tags strictfipsruntime"
 
-FROM registry.ci.openshift.org/ocp/4.20:base-rhel9
+FROM registry.ci.openshift.org/ocp/4.21:base-rhel9
 
 USER 1001