Allow Box4 (#676)

Author: theofidry

composer.json

@@ -34,7 +34,7 @@
     },
     "require-dev": {
         "bamarni/composer-bin-plugin": "^1.1",
-        "humbug/box": "^3.16.0",
+        "humbug/box": "^3.16.0 || ^4.0",
         "phpspec/prophecy-phpunit": "^2.0",
         "phpunit/phpunit": "^9.0"
     },