Stop guessing notification type

Before the search term was either:
- an email address (or partial email address)
- a phone number (or partial phone number)

Now it can also be:
- a reference (or partial reference)

We can take a pretty good guess, by looking at the search term, whether
the thing the user is searching by email address or phone number. This
helps us:
- only show relevant notifications
- normalise the search term to give the best chance of matching what we
  store in the `normalised_to` field

However we can’t look at a search term and guess whether it’s a
reference, because a reference could take any format. Therefore if the
user hasn’t told us what kind of thing their search term is, we should
stop trying to guess.

app/service/rest.py

@@ -455,7 +455,7 @@ def cancel_notification_for_service(service_id, notification_id):
 
 
 def search_for_notification_by_to_field(service_id, search_term, statuses, notification_type):
-    results = notifications_dao.dao_get_notifications_by_to_field(
+    results = notifications_dao.dao_get_notifications_by_recipient_or_reference(
         service_id=service_id,
         search_term=search_term,
         statuses=statuses,