Update composer.json

"require": "6.3" installed 6.3.0, but we probably want the latest stable 6.3

Author: tacman

composer.json

@@ -101,7 +101,7 @@
     "extra": {
         "symfony": {
             "allow-contrib": true,
-            "require": "6.3"
+            "require": "^6.3"
         }
     }
 }