Switch copyright holder to "Google LLC" (#4287)

diff --git a/nox.py b/nox.py
index b614e46..35c314d 100644
--- a/nox.py
+++ b/nox.py
@@ -1,4 +1,4 @@
-# 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.