Update to the stable version

Author: javiereguiluz

composer.json

@@ -3,7 +3,7 @@
     "license": "MIT",
     "type": "project",
     "description": "Symfony Demo Application",
-    "minimum-stability": "dev",
+    "minimum-stability": "stable",
     "prefer-stable": true,
     "replace": {
         "symfony/polyfill-php72": "*",