Update composer.json : fix flex version

Author: anoziere

composer.json

@@ -4,7 +4,7 @@
   "license": "LGPL-3.0+",
   "require": {
     "thelia/thelia-skeleton": "~2.5.5",
-    "symfony/flex": "^1.19",
+    "symfony/flex": "^2.4",
     "thelia/frontoffice-modern-template": "~2.5.5",
     "thelia/open-api-module": "^2.2",
     "thelia/smarty-redirection-module": "~2.0.0",