Updating marketplace-operator images to be consistent with ART

Reconciling with https://github.com/openshift/ocp-build-data/tree/0c10ae924af72f1c759cf8b24b50de94c02e6268/images/marketplace-operator.yml

Author: AOS Automation Release Team

Diff for: Dockerfile.rhel7

@@ -1,10 +1,10 @@
 
-FROM registry.svc.ci.openshift.org/ocp/builder:rhel-8-golang-1.15-openshift-4.6 AS builder
+FROM registry.ci.openshift.org/ocp/builder:rhel-8-golang-1.16-openshift-4.8 AS builder
 WORKDIR /go/src/github.com/operator-framework/operator-marketplace
 COPY . .
 RUN make osbs-build
 
-FROM registry.svc.ci.openshift.org/ocp/4.6:base
+FROM registry.ci.openshift.org/ocp/4.8:base
 RUN useradd marketplace-operator
 USER marketplace-operator
 COPY --from=builder /go/src/github.com/operator-framework/operator-marketplace/build/_output/bin/marketplace-operator /usr/bin