Update more extension manifests to manifest_version 2

chrome/test/data/extensions/hosted_app/manifest.json

 {
   "name": "hosted_app",
   "version": "0.1",
+  "manifest_version": 2,
   "description": "Trivial hosted app.",
   "app": {
     "urls": [
       "http://localhost/files/extensions/hosted_app/main.html"
     ],
     "launch": {
       "web_url": "http://localhost/files/extensions/hosted_app/main.html"
     }
   }
 }