Remove domains from branding forms

We’re deprecating storing the domain as text on a branding in favour of
a database relationship between branding and organisation.

We need to do this now in order to remove the validation on these fields
(which depends on the data in `domains.yml`)

app/main/validators.py

@@ -11,7 +11,7 @@ from wtforms.validators import Email
 
 from app import formatted_list
 from app.main._blacklisted_passwords import blacklisted_passwords
-from app.utils import AgreementInfo, Spreadsheet, is_gov_user
+from app.utils import Spreadsheet, is_gov_user
 
 
 class Blacklist:
@@ -111,34 +111,3 @@ class DoesNotStartWithDoubleZero:
     def __call__(self, form, field):
         if field.data and field.data.startswith("00"):
             raise ValidationError(self.message)
-
-
-class KnownGovernmentDomain:
-
-    message = 'Not a known government domain (you might need to update domains.yml)'
-
-    def __call__(self, form, field):
-        if field.data and AgreementInfo(field.data).owner is None:
-            raise ValidationError(self.message)
-
-
-class CanonicalGovernmentDomain:
-
-    message = 'Not {} domain (use {} if appropriate)'
-
-    def __call__(self, form, field):
-
-        if not field.data:
-            return
-
-        domain = AgreementInfo(field.data)
-
-        if not domain.is_canonical:
-            raise ValidationError(
-                self.message.format('a canonical', domain.canonical_domain)
-            )
-
-        if field.data != domain.canonical_domain:
-            raise ValidationError(
-                self.message.format('an organisation-level', domain.canonical_domain)
-            )