Auto-update dependencies. [(#1377)](GoogleCloudPlatform/python-docs-samples#1377)

* Auto-update dependencies.

* Update requirements.txt

Author: dpebot

samples/appengine/flexible/tasks/requirements.txt

@@ -2,5 +2,5 @@ Flask==0.12.2
 google-api-python-client==1.6.5
 google-auth==1.4.1
 google-auth-httplib2==0.0.3
-google-cloud-datastore==1.5.0
+google-cloud-datastore==1.6.0
 gunicorn==19.7.1