Change targetBoxVersion to 0.4.0

CloudronManifest.json

@@ -30,6 +30,6 @@
     "http://gogs.io/imgs/screenshoots/5.png"
   ],
   "tags": [ "version control", "git", "code hosting", "development" ],
-  "targetBoxVersion": "0.0.66",
+  "targetBoxVersion": "0.4.0",
   "changelog": "file://CHANGELOG"
 }