[2.2.x] Fixed #30330 -- Fixed setting of primary key to None during fast-delete.

Regression in bc7dd8490b.

Backport of afc708cf6d from master

django/db/models/deletion.py

@@ -278,6 +278,7 @@ class Collector:
             if self.can_fast_delete(instance):
                 with transaction.mark_for_rollback_on_error():
                     count = sql.DeleteQuery(model).delete_batch([instance.pk], self.using)
+                setattr(instance, model._meta.pk.attname, None)
                 return count, {model._meta.label: count}
 
         with transaction.atomic(using=self.using, savepoint=False):