forms: remove old mixin (#68204)

src/authentic2_auth_fedict/forms.py

@@ -14,13 +14,12 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from authentic2.apps.authenticators.forms import AuthenticatorFormMixin
 from django import forms
 
 from .models import FedictAuthenticator
 
 
-class FedictAuthenticatorForm(AuthenticatorFormMixin, forms.ModelForm):
+class FedictAuthenticatorForm(forms.ModelForm):
     class Meta:
         model = FedictAuthenticator
         exclude = ('name', 'slug', 'ou')