minor #9536 Fix "JsonSerializable" URL (liviubalan, Liviu Balan)

This PR was merged into the 3.4 branch.

Discussion
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Fix "JsonSerializable" URL

Change generated URL "http://api.symfony.com/3.4/JsonSerializable.html" to "http://php.net/manual/en/class.jsonserializable.php"

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Commits
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fbd87a6 Changes after code review
5116cc3 Fix "JsonSerializable" URL

Author: javiereguiluz

serializer.rst

@@ -103,7 +103,7 @@ As well as the following normalizers:
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\DataUriNormalizer` to
   transform :phpclass:`SplFileInfo` objects in `Data URIs`_
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\JsonSerializableNormalizer`
-  to deal with objects implementing the :class:`JsonSerializable` interface
+  to deal with objects implementing the :phpclass:`JsonSerializable` interface
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\ArrayDenormalizer` to
   denormalize arrays of objects using a format like `MyObject[]` (note the `[]` suffix)