Update more extension manifests to manifest_version 2

chrome/test/data/extensions/isolated_apps/app2/manifest.json

 {
   "name": "isolated_app2",
   "version": "0.1",
+  "manifest_version": 2,
   "description": "Tests isolation of stored data for apps.",
   "app": {
     "urls": [
       "http://localhost/files/extensions/isolated_apps/app2"
     ],
     "launch": {
       "web_url": "http://localhost/files/extensions/isolated_apps/app2/main.html"
     },
     "isolation": [
       "storage"
     ]
   },
   "permissions": [
     "experimental"
   ]
 }