Move another set of extension tests to manifest_version 2

chrome/test/data/extensions/api_test/tabs/connect/manifest.json

 {
   "name": "chrome.tabs",
   "version": "0.1",
+  "manifest_version": 2,
   "description": "end-to-end browser test for chrome.tab.connect API",
   "background_page": "test.html",
   "content_scripts": [
     {
       "matches": ["http://*/*"],
       "js": ["echo.js"]
     }
   ],
   "permissions": ["tabs"]
 }