missing header (#1665)

Author: pjfanning

.github/workflows/build-test-prValidation.yml

@@ -1,3 +1,11 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# license agreements; and to You under the Apache License, version 2.0:
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# This file is part of the Apache Pekko project, which was derived from Akka.
+#
+
 name: Pull Requests
 
 on: