Remove unused test code

Notifications don't have a `scheduled_for` attribute, and the test
function deleted isn't used anywhere.

tests/app/billing/test_billing.py

@@ -29,10 +29,6 @@ IN_MAY_2016 = datetime(2016, 5, 10, 23, 00, 00)
 IN_JUN_2016 = datetime(2016, 6, 3, 23, 00, 00)
 
 
-def _assert_dict_equals(actual, expected_dict):
-    assert actual == expected_dict
-
-
 def test_create_update_free_sms_fragment_limit_invalid_schema(client, sample_service):
 
     response = client.post('service/{}/billing/free-sms-fragment-limit'.format(sample_service.id),

tests/app/db.py

@@ -260,7 +260,6 @@ def create_notification(
         rate_multiplier=None,
         international=False,
         phone_prefix=None,
-        scheduled_for=None,
         normalised_to=None,
         one_off=False,
         reply_to_text=None,

tests/app/v2/notifications/test_get_notifications.py

@@ -20,7 +20,6 @@ def test_get_notification_by_id_returns_200(
         template=sample_template,
         billable_units=billable_units,
         sent_by=provider,
-        scheduled_for="2017-05-12 15:15"
     )
 
     # another
@@ -28,7 +27,6 @@ def test_get_notification_by_id_returns_200(
         template=sample_template,
         billable_units=billable_units,
         sent_by=provider,
-        scheduled_for="2017-06-12 15:15"
     )
 
     auth_header = create_service_authorization_header(service_id=sample_notification.service_id)