fix: change license header for pom.xml

Author: Alan5142

appengine-java21/ee8/mail/pom.xml

@@ -1,5 +1,5 @@
 <!--
-Copyright 2016 Google Inc.
+Copyright 2016 Google LLC
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.