KeepMethodDecorator adds ? to mixed param type when transfering kept method

Which makes it unusable -> fix this asap

First run: public static function fromDTO(mixed $dto): static
Second run: public static function fromDTO(?mixed $dto): static

It is bug in nette/php-generator: https://github.com/nette/php-generator/issues/74

Fixed in 3.5.2

mentioned in merge request !28 (merged)

closed with merge request !28 (merged)

mentioned in commit 8f1c68ea