linting fixes

Author: ndench

serializer/custom_normalizer.rst

@@ -74,11 +74,9 @@ follows:
   result is not cacheable.
 - A ``null`` value for a type means that the normalizer or denormalizer does not support that type.
 
-Here is an example of how to use the ``getSupportedTypes()`` method:
+Here is an example of how to use the ``getSupportedTypes()`` method::
 
-.. code-block:: php
-
-    use Symfony\\Component\\Serializer\\Normalizer\\NormalizerInterface;
+    use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
 
     class MyNormalizer implements NormalizerInterface
     {