Added missing older version for the symfony/event-dispatcher package

Author: Willem Oostendorp

composer.json

@@ -7,7 +7,7 @@
         "php": ">=5.5.9",
         "symfony/workflow": "^3.3 || ^4.0",
         "symfony/process": "^3.3 || ^4.0",
-        "symfony/event-dispatcher": "^4.0",
+        "symfony/event-dispatcher": "^3.3 || ^4.0",
         "illuminate/console": "5.3.* || 5.4.* || 5.5.* || 5.6.*",
         "illuminate/support": "5.3.* || 5.4.* || 5.5.* || 5.6.*"
     },