docs(copyright): correct name of company for commits after 2015 (#440)

diff --git a/tests/test_iam.py b/tests/test_iam.py
index 52ab9bd..c98a138 100644
--- a/tests/test_iam.py
+++ b/tests/test_iam.py
@@ -1,4 +1,4 @@
-# Copyright 2017 Google Inc.
+# Copyright 2017 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.