minor #13754 Fix supportsNormalization parameters definition (mathieu-ducrot)

This PR was merged into the 4.4 branch.

Discussion
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Fix supportsNormalization parameters definition

## Description

Add **$context** parameter in code example which is needed in Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface supportsNormalization definition.

In 3.4 documentation this was not needed because the example code implements NormalizerInterface vs ContextAwareNormalizerInterface since 4.4.

Commits
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f3b4364 Fix supportsNormalization parameters definition

Author: javiereguiluz

serializer/custom_normalizer.rst

@@ -47,7 +47,7 @@ to customize the normalized data. To do that, leverage the ``ObjectNormalizer``:
             return $data;
         }
 
-        public function supportsNormalization($data, $format = null)
+        public function supportsNormalization($data, $format = null, array $context = [])
         {
             return $data instanceof Topic;
         }