bug #5412 Update serializer.rst (mantulo)

This PR was merged into the 2.7 branch.

Discussion
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Update serializer.rst

fixed misprint

Commits
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edc33a8 Update serializer.rst

Author: wouterj

components/serializer.rst

@@ -185,7 +185,7 @@ like the following::
 
     use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
     // For annotations
-    usr Doctrine\Common\Annotations\AnnotationReader;
+    use Doctrine\Common\Annotations\AnnotationReader;
     use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;
     // For XML
     // use Symfony\Component\Serializer\Mapping\Loader\XmlFileLoader;