Fix deprecation in SF 6.1

[raziel057]

Fix the following deprecation:

The "FOS\RestBundle\Serializer\Normalizer\FormErrorNormalizer::supportsNormalization()" method will require a new "array $context" argument in the next major version of its interface "Symfony\Component\Serializer\Normalizer\NormalizerInterface", not defining it is deprecated.

The "FOS\RestBundle\Serializer\Normalizer\FlattenExceptionNormalizer" class implements "Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface" that is deprecated since symfony/serializer 6.1, use NormalizerInterface instead.