remove minBoxVersion

CloudronManifest.json

@@ -25,6 +25,5 @@
     "https://wordpress.org/about/shots/1.5/front-5.png",
     "https://wordpress.org/about/shots/1.5/front-3.png"
  ],
- "changelog": "file://CHANGELOG",
- "minBoxVersion": "0.13.3"
+ "changelog": "file://CHANGELOG"
 }