remove most letter branding

tests/app/db.py

@@ -46,7 +46,6 @@ from app.models import (
     InvitedOrganisationUser,
     InvitedUser,
     Job,
-    LetterBranding,
     LetterRate,
     Notification,
     NotificationHistory,
@@ -931,15 +930,6 @@ def create_template_folder(service, name='foo', parent=None):
     return tf
 
 
-def create_letter_branding(name='HM Government', filename='hm-government'):
-    test_domain_branding = LetterBranding(name=name,
-                                          filename=filename,
-                                          )
-    db.session.add(test_domain_branding)
-    db.session.commit()
-    return test_domain_branding
-
-
 def set_up_usage_data(start_date):
     year = int(start_date.strftime('%Y'))
     one_week_earlier = start_date - timedelta(days=7)