update google-api-python-client to 1.8.3 final part [(#3827)](GoogleCloudPlatform/python-docs-samples#3827)

Author: leahecole

samples/snippets/api/requirements.txt

@@ -1,3 +1,3 @@
-google-api-python-client==1.8.2
+google-api-python-client==1.8.3
 google-auth==1.15.0
 google-auth-httplib2==0.0.3