[FIX] auth_totp: User deletion

* Add ondelete='cascade' to the res.users.authenticator.create wizard model to
properly support deletion of users who have just created an MFA authenticator

auth_totp/wizards/res_users_authenticator_create.py

@@ -47,6 +47,7 @@ class ResUsersAuthenticatorCreate(models.TransientModel):
              ' will be tied to',
         readonly=True,
         index=True,
+        ondelete='cascade',
     )
     confirmation_code = fields.Char(
         string='Confirmation Code',