Updating Dockerfile.rhel7 baseimages to mach ocp-build-data config

This PR is autogenerated by the [ocp-build-data-enforcer][1].
It updates the baseimages in the Dockerfile used for promotion in order to ensure it
matches the configuration in the [ocp-build-data repository][2] used
for producing release artifacts.

If you believe the content of this PR is incorrect, please contact the dptp team in
#forum-testplatform.

[1]: https://github.com/openshift/ci-tools/tree/master/cmd/ocp-build-data-enforcer
[2]: https://github.com/openshift/ocp-build-data/tree/openshift-4.6-rhel-8/images

Author: openshift-bot

Dockerfile.rhel7

@@ -1,11 +1,11 @@
-FROM registry.svc.ci.openshift.org/ocp/builder:golang-1.14 AS builder
+FROM registry.svc.ci.openshift.org/ocp/builder:rhel-8-golang-openshift-4.6 AS builder
 WORKDIR /go/src/github.com/openshift/cluster-version-operator
 COPY . .
 RUN hack/build-go.sh; \
     mkdir -p /tmp/build; \
     cp _output/linux/$(go env GOARCH)/cluster-version-operator /tmp/build/cluster-version-operator
 
-FROM registry.svc.ci.openshift.org/ocp/4.0:base
+FROM registry.svc.ci.openshift.org/ocp/4.6:base
 COPY --from=builder /tmp/build/cluster-version-operator /usr/bin/
 COPY install /manifests
 COPY vendor/github.com/openshift/api/config/v1/0000_00_cluster-version-operator_01_clusterversion.crd.yaml /manifests/