Tell users that they can search whole postal address

We’re now normalising and storing the whole address in the
`normalised_to` field. Previously we were only storing the first line
of the address.

Enough time should now have passed that the field will have been
populated for all letters in the database.

Thus we can now tell users that it’s not just the first line they can
search by.

app/main/views/jobs.py

@@ -171,9 +171,7 @@ def view_notifications(service_id, message_type=None):
         things_you_can_search_by={
             'email': ['email address'],
             'sms': ['phone number'],
-            # This should become ‘postal address’ not ‘first line…’ once
-            # we’ve finished populating normalised addresses
-            'letter': ['first line of address', 'file name'],
+            'letter': ['postal address', 'file name'],
             # We say recipient here because combining all 3 types, plus
             # reference gets too long for the hint text
             None: ['recipient'],