minor #16683 [Serializer] Update serializer.rst (issamkhadiri1989)

This PR was submitted for the 6.0 branch but it was merged into the 6.4 branch instead.

Discussion
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[Serializer] Update serializer.rst

Hello

I think it is not necessary to add a ClassMetadataFactory here because we are not about to use Class Metadata, Without that argument, the example works well too

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Commits
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2d93c37 Update serializer.rst

Author: javiereguiluz

components/serializer.rst

@@ -1722,7 +1722,7 @@ context option::
         }
     }
 
-    $normalizer = new ObjectNormalizer($classMetadataFactory);
+    $normalizer = new ObjectNormalizer();
     $serializer = new Serializer([$normalizer]);
 
     $data = $serializer->denormalize(