Change base image for openshift platform

This will change the base image used for image builds
issue of webhook image failing on openshift because of non root
and require 65532 user is also fixed

Author: piyush-garg

.ko.yaml

@@ -1 +1,4 @@
 defaultBaseImage: gcr.io/distroless/static:nonroot
+baseImageOverrides:
+  github.com/tektoncd/operator/cmd/openshift/operator: registry.access.redhat.com/ubi8/ubi-minimal
+  github.com/tektoncd/operator/cmd/openshift/webhook: registry.access.redhat.com/ubi8/ubi-minimal