is_granted twig reference points to deprecated functionality

[tbs-trappy]

is_granted is documented as supporting string[], however, according to this issue I submitted, that functionality was deprecated in Symfony 4.0. It currently only supports single inputs ("string", vs. "string, string[]")

Link:
https://symfony.com/doc/current/reference/twig_reference.html#is-granted

Discussion:
symfony/symfony#37132