Update phpstan/phpstan-webmozart-assert requirement
Update phpstan/phpstan-webmozart-assert requirement

Updates the requirements on [phpstan/phpstan-webmozart-assert](https://github.com/phpstan/phpstan-webmozart-assert) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan-webmozart-assert/releases)
- [Commits](https://github.com/phpstan/phpstan-webmozart-assert/compare/0.12.7...0.12.8)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
Sylius/Sylius-Standard,Sylius/Sylius-Standard,Sylius/Sylius-Standard