grumphp should be a dev dependency

composer.json

@@ -13,7 +13,6 @@
     "jawira/case-converter": "^3.4",
     "mathmarques/smarty-view": "^1.1",
     "npm-asset/open-sans-fontface": "^1.4",
-    "phpro/grumphp": "^0.18.0",
     "rinvex/countries": "^6.1",
     "symfony/process": "^4.0",
     "symfony/translation": "^4.0",
@@ -26,6 +25,7 @@
     "ffmpeg/ffmpeg": "^4.1",
     "heroku/heroku-buildpack-php": "^162.0",
     "php-mock/php-mock-mockery": "^1.3",
+    "phpro/grumphp": "^0.18.0",
     "phpstan/phpstan": "^0.12.25",
     "phpunit/phpunit": "^8.4",
     "roave/security-advisories": "dev-master",