The Entity type filter still expects an enum in the Django admin

Sentry Issue: ARKINDEX-BACKEND-1EE

AttributeError: 'ForeignKey' object has no attribute 'enum'
(8 additional frame(s) were not displayed)
...
  File "django/contrib/admin/options.py", line 1931, in changelist_view
    cl = self.get_changelist_instance(request)
  File "django/contrib/admin/options.py", line 834, in get_changelist_instance
    return ChangeList(
  File "django/contrib/admin/views/main.py", line 122, in __init__
    self.queryset = self.get_queryset(request)
  File "django/contrib/admin/views/main.py", line 507, in get_queryset
    new_qs = filter_spec.queryset(request, qs)
  File "enumfields/admin.py", line 23, in queryset
    self.field.enum(self.lookup_val)

An EnumFieldListFilter is being used for the Django admin's entity type filter, but the entity type is now a separate model. This really shows how much we use the Django admin in dev.