Merge branch '5.4' into 6.4

* 5.4:
  add missing use statement

Author: javiereguiluz

components/serializer.rst

@@ -382,6 +382,7 @@ Then, create your groups definition:
 
 You are now able to serialize only attributes in the groups you want::
 
+    use Acme\MyObj;
     use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
     use Symfony\Component\Serializer\Serializer;