Consistency with other quickstarts (#1229)

For consistency with the other quickstarts, adjust this one to use manual scaling as well.

Author: devlance

appengine/flexible/hello_world/app.yaml

@@ -9,8 +9,8 @@ runtime_config:
 # The settings below are to reduce costs during testing and are not appropriate
 # for production use. For more information, see:
 # https://cloud.google.com/appengine/docs/flexible/python/configuring-your-app-with-app-yaml
-automatic_scaling:
-  max_num_instances: 1
+manual_scaling:
+  instances: 1
 resources:
   cpu: 1
   memory_gb: 0.5