Don’t create new organisations with no crown status

We need the crown status set so that we can let them accept the
agreement online.

app/main/forms.py

@@ -596,10 +596,13 @@ class OrganisationTypeForm(StripWhitespaceForm):
 
 class NewOrganisationForm(
     RenameOrganisationForm,
-    OrganisationTypeForm,
+    OrganisationOrganisationTypeForm,
     OrganisationCrownStatusForm,
 ):
-    pass
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        # Don’t offer the ‘not sure’ choice
+        self.crown_status.choices = self.crown_status.choices[:-1]
 
 
 class FreeSMSAllowance(StripWhitespaceForm):

tests/app/main/views/organisations/test_organisation.py

@@ -93,7 +93,6 @@ def test_page_to_create_new_organisation(
         ('radio', 'organisation_type', 'nhs'),
         ('radio', 'crown_status', 'crown'),
         ('radio', 'crown_status', 'non-crown'),
-        ('radio', 'crown_status', 'unknown'),
         ('hidden', 'csrf_token', ANY),
     ]