Updating coredns-container image to be consistent with ART

Reconciling with https://github.com/openshift/ocp-build-data/tree/c78b2b27f47b41d5d59449c863f3dea6eaa988b7/images/coredns.yml

.ci-operator.yaml

@@ -1,4 +1,4 @@
 build_root_image:
   name: release
   namespace: openshift
-  tag: rhel-8-release-golang-1.20-openshift-4.15
+  tag: rhel-9-release-golang-1.21-openshift-4.16

Dockerfile.openshift.rhel7

@@ -1,9 +1,9 @@
-FROM registry.ci.openshift.org/ocp/builder:rhel-8-golang-1.20-openshift-4.15 AS builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-9-golang-1.21-openshift-4.16 AS builder
 WORKDIR /go/src/github.com/coredns/coredns
 COPY . .
 RUN GO111MODULE=on GOFLAGS=-mod=vendor go build -o coredns .
 
-FROM registry.ci.openshift.org/ocp/4.15:base
+FROM registry.ci.openshift.org/ocp/4.16:base-rhel9
 COPY --from=builder /go/src/github.com/coredns/coredns/coredns /usr/bin/
 
 ENTRYPOINT ["/usr/bin/coredns"]