Make limit of DAO timeout function more obvious

We're going to iterate how we use the function with a limit, so we
shouldn't say it's "temporary" anymore. We don't need to change the
default, but having it in the function parameters makes it easier to
see the funtion doesn't time out all notifications, just some.

app/dao/notifications_dao.py

@@ -489,7 +489,7 @@ def dao_delete_notifications_by_id(notification_id):
     ).delete(synchronize_session='fetch')
 
 
-def dao_timeout_notifications(cutoff_time):
+def dao_timeout_notifications(cutoff_time, limit=100000):
     """
     Set email and SMS notifications (only) to "temporary-failure" status
     if they're still sending from before the specified cutoff_time.
@@ -498,15 +498,11 @@ def dao_timeout_notifications(cutoff_time):
     current_statuses = [NOTIFICATION_SENDING, NOTIFICATION_PENDING]
     new_status = NOTIFICATION_TEMPORARY_FAILURE
 
-    # TEMPORARY: limit the notifications to 100K as otherwise we
-    # see an issues where the task vanishes after it starts executing
-    # - we believe this is a OOM error but there are no logs. From
-    # experimentation we've found we can safely process up to 100K.
     notifications = Notification.query.filter(
         Notification.created_at < cutoff_time,
         Notification.status.in_(current_statuses),
         Notification.notification_type.in_([SMS_TYPE, EMAIL_TYPE])
-    ).limit(100000).all()
+    ).limit(limit).all()
 
     Notification.query.filter(
         Notification.created_at < cutoff_time,