Updating ose-openstack-machine-controllers images to be consistent with ART

Reconciling with https://github.com/openshift/ocp-build-data/tree/da6a5af1fa96762cc8410f09fc28c0457280f59a/images/ose-openstack-machine-controllers.yml

Author: AOS Automation Release Team

.ci-operator.yaml

@@ -1,4 +1,4 @@
 build_root_image:
   name: release
   namespace: openshift
-  tag: rhel-8-release-golang-1.20-openshift-4.14
+  tag: rhel-8-release-golang-1.20-openshift-4.15

Dockerfile.rhel

@@ -1,9 +1,9 @@
-FROM registry.ci.openshift.org/ocp/builder:rhel-8-golang-1.20-openshift-4.14 AS builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-8-golang-1.20-openshift-4.15 AS builder
 WORKDIR /go/src/sigs.k8s.io/cluster-api-provider-openstack
 COPY . .
 
 RUN go build -o ./machine-controller-manager ./cmd/manager
 
-FROM registry.ci.openshift.org/ocp/4.14:base
+FROM registry.ci.openshift.org/ocp/4.15:base
 
 COPY --from=builder /go/src/sigs.k8s.io/cluster-api-provider-openstack/machine-controller-manager /