[4.4] Allow the symfony/flex plugin

Author: alexislefebvre

composer.json

@@ -53,7 +53,10 @@
         "preferred-install": {
             "*": "dist"
         },
-        "sort-packages": true
+        "sort-packages": true,
+        "allow-plugins": {
+            "symfony/flex": true
+        }
     },
     "autoload": {
         "psr-4": {