chore(deps): update dependency google-auth to v1.16.0 [(#3903)](GoogleCloudPlatform/python-docs-samples#3903)

Author: renovate-bot

samples/snippets/api/requirements.txt

@@ -1,3 +1,3 @@
 google-api-python-client==1.8.4
-google-auth==1.15.0
+google-auth==1.16.0
 google-auth-httplib2==0.0.3