Updating ose-cluster-update-keys-container image to be consistent with ART for 4.21

Reconciling with https://github.com/openshift/ocp-build-data/tree/4fbe3fab45239dc4be6f5d9d98a0bf36e0274ec9/images/ose-cluster-update-keys.yml

Author: AOS Automation Release Team

Dockerfile.rhel

@@ -1,4 +1,4 @@
-FROM registry.ci.openshift.org/ocp/4.20:base-rhel9
+FROM registry.ci.openshift.org/ocp/4.21:base-rhel9
 COPY manifests.rhel/ /manifests/
 LABEL description="This image contains the trusted keys for the updates delivered to a cluster." \
       io.openshift.release.operator=true