Set the RHTAP base image to one based on Go 1.21

Signed-off-by: mprahl <[email protected]>

Dockerfile.rhtap

@@ -1,7 +1,7 @@
 # Stage 1: Use image builder to build the target binaries
 # Copyright Contributors to the Open Cluster Management project
 
-FROM brew.registry.redhat.io/rh-osbs/openshift-golang-builder:rhel_8_1.20 AS builder
+FROM brew.registry.redhat.io/rh-osbs/openshift-golang-builder:rhel_9_1.21 AS builder
 
 ENV COMPONENT=governance-policy-propagator
 ENV REPO_PATH=/go/src/github.com/stolostron/${COMPONENT}