Fix: Relax version constraint

Author: localheinz

generator/composer.json

@@ -9,7 +9,7 @@
   "require": {
     "php": "^7.2",
     "ext-simplexml": "*",
-    "ext-json": "^1.5",
+    "ext-json": "*",
     "symfony/console": "^4.1.4",
     "symfony/process": "^4.1",
     "symfony/finder": "^4.1"