chore: Update PHPStan (#178)

Author: theofidry

composer.json

@@ -19,8 +19,8 @@
         "ext-json": "*",
         "composer/composer": "^2.6",
         "phpstan/extension-installer": "^1.1",
-        "phpstan/phpstan": "^1.8",
-        "phpstan/phpstan-phpunit": "^1.1",
+        "phpstan/phpstan": "^1.8 || ^2.0",
+        "phpstan/phpstan-phpunit": "^1.1 || ^2.0",
         "phpunit/phpunit": "^8.5 || ^9.6 || ^10.0",
         "symfony/console": "^2.8.52 || ^3.4.35 || ^4.4 || ^5.0 || ^6.0",
         "symfony/finder": "^2.8.52 || ^3.4.35 || ^4.4 || ^5.0 || ^6.0",