Add Marine Management Organisation as email domain

Seems like sometimes they use a Defra email address, sometimes their
own .org.uk one.

tests/app/main/test_validators.py

@@ -99,6 +99,7 @@ def _gen_mock_field(x):
     'test@bbsrc.ac.uk',
     'test@acas.org.uk',
     'test@biglotteryfund.org.uk',
+    'test@marinemanagement.org.uk',
 ])
 def test_valid_list_of_white_list_email_domains(
     client,