fixup clean admin

No idea why I cant reproduce the bug I had when I made this change

itou/eligibility/admin.py

@@ -15,7 +15,7 @@
 class AbstractSelectedAdministrativeCriteriaInlineFormSet(BaseInlineFormSet):
     def clean(self):
         super().clean()
-        for line in getattr(self, "cleaned_data", []):
+        for line in self.cleaned_data:
             if line.get("DELETE") and line["id"].certified:
                 raise ValidationError("Impossible de supprimer un critère certifié")