UPSTREAM: <carry>: Updating ose-csi-external-resizer-container image to be consistent with ART for 4.21

Reconciling with https://github.com/openshift/ocp-build-data/tree/4fbe3fab45239dc4be6f5d9d98a0bf36e0274ec9/images/ose-csi-external-resizer.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.openshift

@@ -1,8 +1,8 @@
-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/kubernetes-csi/external-resizer
 COPY . .
 RUN make build
 
-FROM registry.ci.openshift.org/ocp/4.20:base-rhel9
+FROM registry.ci.openshift.org/ocp/4.21:base-rhel9
 COPY --from=builder /go/src/github.com/kubernetes-csi/external-resizer/bin/csi-resizer /usr/bin/
 ENTRYPOINT ["/usr/bin/csi-resizer"]