Add return type for accept() method
requested to merge issue/fancy_file_delete-3280336:3280336-php8.1-messagedeprecated-function into 2.0.x
This PR removes the need for #[\ReturnTypeWillChange] and sets boolean as return data type. We know what the data type should be for FancyFileDeleteDirectoryOnlyRecursiveFilterIterator::accept() because it is documented on the parent class (https://www.php.net/manual/en/class.recursivefilteriterator.php).
Closes #3280336