Require ^4.0 for Laravel 5.7 upgrade

Author: AlexMac7

composer.json

@@ -25,7 +25,7 @@
     "php": ">=5.5",
     "ext-curl": "*",
     "jms/serializer": "^1.0",
-    "symfony/event-dispatcher": "^2.3|^3.0",
+    "symfony/event-dispatcher": "^2.3|^4.0",
     "symfony/yaml": "^2.3|^3.0",
     "guzzlehttp/guzzle": "^6.0",
     "doctrine/collections": "^1.2"