Running make test-boilerplate returned the following error so fixed
accordingly

Header in kubernetes-sigs/nfs-subdir-external-provisioner/release-tools/../Dockerfile does not match reference, diff:

--- reference
+++ kubernetes-sigs/nfs-subdir-external-provisioner/release-tools/../Dockerfile
@@ -1,4 +1,4 @@
-# Copyright YEAR The Kubernetes Authors.
+# Copyright YEAR-YEAR The Kubernetes Authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.