minor symfony#8301 Update serializer.rst (VisionPages)

This PR was submitted for the 3.3 branch but it was merged into the 2.7 branch instead (closes symfony#8301).

Discussion
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Update serializer.rst

Commits
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07a0d2a Update serializer.rst

Author: xabbuh

components/serializer.rst

@@ -395,7 +395,7 @@ class extending :class:`Symfony\\Component\\Serializer\\Normalizer\\AbstractNorm
 including :class:`Symfony\\Component\\Serializer\\Normalizer\\GetSetMethodNormalizer`
 and :class:`Symfony\\Component\\Serializer\\Normalizer\\PropertyNormalizer`::
 
-    use Symfony\Component\Serializer\Encoder\JsonEncoder
+    use Symfony\Component\Serializer\Encoder\JsonEncoder;
     use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
     use Symfony\Component\Serializer\Serializer;