[Serializer] Fix CS

Author: dunglas

components/serializer.rst

@@ -160,10 +160,10 @@ Assume you have the following object plain-old-PHP object::
     }
 
 The definition of serialization can be specified using annotations, XML
-or YAML. The :class:`Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory`
+or YAML. The :class:`Symfony\\Component\\Serializer\\Mapping\\Factory\\ClassMetadataFactory`
 that will be used by the normalizer must be aware of the format to use.
 
-Initialize the :class:`Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory`
+Initialize the :class:`Symfony\\Component\\Serializer\\Mapping\\Factory\\ClassMetadataFactory`
 like the following::
 
     use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
@@ -197,6 +197,7 @@ Then, create your groups definition:
              * @Groups({"group1", "group2"})
              */
             public $foo;
+
             /**
              * @Groups({"group3"})
              */