Update utils to 12.0.0

Includes:

- [x] https://github.com/alphagov/notifications-utils/pull/94 (breaking
      changes which are responsible for all the changes to the API in
      this PR)

The test for `get_sms_fragment_count` has been removed because this
method is already tested in utils here:

ac20f7e99e/tests/test_base_template.py (L140-L159)

tests/app/dao/test_notification_dao.py

@@ -42,8 +42,6 @@ from app.dao.notifications_dao import (
     dao_timeout_notifications,
     get_financial_year)
 
-from notifications_utils.template import get_sms_fragment_count
-
 from tests.app.conftest import (sample_notification, sample_template, sample_email_template, sample_service, sample_job,
                                 sample_api_key)
 
@@ -821,22 +819,6 @@ def test_should_limit_notifications_return_by_day_limit_plus_one(notify_db, noti
     assert len(all_notifications) == 2
 
 
-@pytest.mark.parametrize(
-    "char_count, expected_sms_fragment_count",
-    [
-        (159, 1),
-        (160, 1),
-        (161, 2),
-        (306, 2),
-        (307, 3),
-        (459, 3),
-        (460, 4),
-        (461, 4)
-    ])
-def test_sms_fragment_count(char_count, expected_sms_fragment_count):
-    assert get_sms_fragment_count(char_count) == expected_sms_fragment_count
-
-
 def test_creating_notification_adds_to_notification_history(sample_template):
     data = _notification_json(sample_template)
     notification = Notification(**data)