Move another set of extension tests to manifest_version 2

chrome/test/data/extensions/api_test/socket/api/manifest.json

 {
   "name": "chrome.socket",
   "version": "0.1",
+  "manifest_version": 2,
   "description": "end-to-end browser test for chrome.experimental.socket API",
   "platform_app": true,
   "background_page": "background.html",
   "app": {
     "launch": {
       "container": "panel",
       "local_path": "main.html"
     }
   },
   "permissions": [
     "experimental",
     "socket"
   ]
 }