fix instance forget original map

Author: nekufa

src/Repository.php

@@ -235,6 +235,7 @@ public function forget(int $id): self
             $instance = $this->persisted[$id];
             unset($this->keys[$instance]);
             unset($this->persisted[$id]);
+            unset($this->original[$id]);
             $this->flushCache();
         }