Remove image-builder-fmt param from Dockerfile Generator to fall back to default (#653)

Co-authored-by: Christoph Stäbler <cstabler@redhat.com>

Author: openshift-cherrypick-robot

openshift/generate.sh

@@ -9,5 +9,4 @@ GOFLAGS='' go install github.com/openshift-knative/hack/cmd/generate@latest
 
 $(go env GOPATH)/bin/generate \
   --root-dir "${repo_root_dir}" \
-  --generators dockerfile \
-  --dockerfile-image-builder-fmt "registry.ci.openshift.org/openshift/release:rhel-8-release-golang-%s-openshift-4.17"
+  --generators dockerfile