Simplify bootstrap and standardize phpunit config

Remove phpunit and require_once unnecessary

Author: JeremieMercier

composer.json

@@ -10,8 +10,7 @@
         "php-parallel-lint/php-parallel-lint": "^1.4",
         "phpstan/extension-installer": "^1.4",
         "phpstan/phpstan": "^2.1",
-        "phpstan/phpstan-deprecation-rules": "^2.0",
-        "phpunit/phpunit": "^9.6"
+        "phpstan/phpstan-deprecation-rules": "^2.0"
     },
     "config": {
         "optimize-autoloader": true,