Adding Highways England to allowed domains tests

tests/app/main/test_validators.py

@@ -102,6 +102,7 @@ def _gen_mock_field(x):
     'test@marinemanagement.org.uk',
     'test@britishmuseum.org',
     'test@derrystrabane.com',
+    'test@highwaysengland.co.uk',
 ])
 def test_valid_list_of_white_list_email_domains(
     client,