Drop postage constraints

The constaints on notifications and notification_history have already
been dropped in production, but still exist in staging and in dev
environments.

The constraints on templates and templates_history exist in all
environments.

tests/app/dao/test_templates_dao.py

@@ -1,7 +1,6 @@
 from datetime import datetime
 
 from freezegun import freeze_time
-from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.orm.exc import NoResultFound
 import pytest
 
@@ -485,37 +484,3 @@ def test_get_template_versions_is_empty_for_hidden_templates(sample_service):
     )
     versions = dao_get_template_versions(service_id=sample_template.service_id, template_id=sample_template.id)
     assert len(versions) == 0
-
-
-@pytest.mark.parametrize("template_type,postage", [('letter', 'third'), ('sms', 'second')])
-def test_template_postage_constraint_on_create(sample_service, sample_user, template_type, postage):
-    data = {
-        'name': 'Sample Template',
-        'template_type': template_type,
-        'content': "Template content",
-        'service': sample_service,
-        'created_by': sample_user,
-        'postage': postage
-    }
-    template = Template(**data)
-    with pytest.raises(expected_exception=SQLAlchemyError):
-        dao_create_template(template)
-
-
-def test_template_postage_constraint_on_update(sample_service, sample_user):
-    data = {
-        'name': 'Sample Template',
-        'template_type': "letter",
-        'content': "Template content",
-        'service': sample_service,
-        'created_by': sample_user,
-        'postage': 'second'
-    }
-    template = Template(**data)
-    dao_create_template(template)
-    created = dao_get_all_templates_for_service(sample_service.id)[0]
-    assert created.name == 'Sample Template'
-
-    created.postage = 'third'
-    with pytest.raises(expected_exception=SQLAlchemyError):
-        dao_update_template(created)