Update more extension manifests to manifest_version 2

chrome/test/data/extensions/effective_host_permissions/two_content_scripts.json

 {
   "name": "effective host permisions test",
   "version": "1.0",
+  "manifest_version": 2,
   "permissions": [
     "http://*.google.com/",
     "http://google.com/",
     "https://google.com/"
   ],
   "content_scripts": [
     {
       "matches": ["http://www.reddit.com/", "http://news.ycombinator.com/"],
       "js": ["foo.js"]
     }
   ]
 }