minor #13499 Update serializer.rst (amine-betari)

This PR was merged into the 4.4 branch.

Discussion
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Update serializer.rst

Add the path correctly for the Person model

Commits
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66c0275 Update serializer.rst

Author: javiereguiluz

components/serializer.rst

@@ -126,7 +126,7 @@ exists in your project::
 Now, if you want to serialize this object into JSON, you only need to
 use the Serializer service created before::
 
-    $person = new App\Model\Person();
+    $person = new \App\Model\Person();
     $person->setName('foo');
     $person->setAge(99);
     $person->setSportsperson(false);