remove dvla_organisation and other unused things

dvla_organisation, branding_dict, a weird `branding` property on
update_service. all gone 💥

app/main/forms.py

@@ -886,27 +886,6 @@ class CreateOrUpdateOrganisation(StripWhitespaceForm):
     name = StringField('Name', validators=[DataRequired()])
 
 
-class LetterBranding(StripWhitespaceForm):
-
-    def __init__(self, choices=[], *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self.dvla_org_id.choices = list(sorted(
-            choices,
-            key=lambda choice: (
-                choice[0] != kwargs.get('dvla_org_id'),
-                choice[0] != '001',
-                choice[1],
-            ),
-        ))
-
-    dvla_org_id = RadioField(
-        'Which logo should this service’s letter have?',
-        validators=[
-            DataRequired()
-        ]
-    )
-
-
 class EmailFieldInWhitelist(EmailField, StripWhitespaceStringField):
     pass
 

app/main/views/service_settings.py

@@ -31,7 +31,6 @@ from app.main.forms import (
     ConfirmPasswordForm,
     FreeSMSAllowance,
     InternationalSMSForm,
-    LetterBranding,
     LinkOrganisationsForm,
     OrganisationTypeForm,
     RenameServiceForm,
@@ -55,7 +54,6 @@ from app.main.forms import (
 from app.utils import (
     AgreementInfo,
     email_safe,
-    get_logo_cdn_domain,
     user_has_permissions,
     user_is_gov_user,
     user_is_platform_admin,
@@ -775,7 +773,6 @@ def service_set_email_branding(service_id):
     return render_template(
         'views/service-settings/set-email-branding.html',
         form=form,
-        branding_dict=get_branding_as_dict(email_branding),
         search_form=SearchTemplatesForm(),
         show_search_box=(len(email_branding) > 6)
     )
@@ -961,15 +958,6 @@ def get_branding_as_value_and_label(email_branding):
     ]
 
 
-def get_branding_as_dict(email_branding):
-    return {
-        branding['id']: {
-            'logo': 'https://{}/{}'.format(get_logo_cdn_domain(), branding['logo']),
-            'colour': branding['colour']
-        } for branding in email_branding
-    }
-
-
 def convert_dictionary_to_wtforms_choices_format(dictionary, value, label):
     return [
         (item[value], item[label]) for item in dictionary