Change timeout-notifications to run every hour

There's no logical constraint that prevents this:

- ft_billing is unaffected by the status updates

- ft_notification_status will still be computed using the updated
statuses for the past day.

Running the task more frequently should limit the maximum number
of notifications it's likely to process.

app/config.py

@@ -251,7 +251,7 @@ class Config(object):
             # app/celery/nightly_tasks.py
             'timeout-sending-notifications': {
                 'task': 'timeout-sending-notifications',
-                'schedule': crontab(hour=0, minute=5),
+                'schedule': crontab(minute=5),
                 'options': {'queue': QueueNames.PERIODIC}
             },
             'create-nightly-billing': {