Switch in box ChromeVox to use new background page.

chrome/browser/resources/chromeos/chromevox/manifest.json.jinja2

 {
 {%if key is defined %}
   "key": "{{key}}",
 {% endif %}
   "manifest_version": 2,
   "name": "__MSG_CHROMEVOX_NAME__",
   "version": "{{set_version}}",
   "description": "__MSG_CHROMEVOX_DESCRIPTION__",
 {% if is_guest_manifest == '1' %}
   "incognito": "split",
 {% endif %}
   "background": {
-{% if is_chromevox_next == '1' %}
     "page": "cvox2/background/background.html"
-{% else %}
-    "page": "chromevox/background/background.html"
-{% endif %}
   },
   "permissions": [
     "accessibilityPrivate",
     "bookmarks",
     "brailleDisplayPrivate",
-{% if is_chromevox_next == '1' %}
     "commands.accessibility",
-{% endif %}
     "commandLinePrivate",
     "experimental",
     "history",
     "storage",
     "systemPrivate",
     "tabs",
     "tts",
     "virtualKeyboardPrivate",
     "<all_urls>"
   ],
@@ skipping 15 matching lines @@
 {% endif %}
       ]
     }
   ],
   "web_accessible_resources": [
     "chromevox/injected/api.js",
     "chromevox/injected/api_util.js",
     "chromevox/injected/mathjax.js",
     "chromevox/injected/mathjax_external_util.js"
   ],
-{% if is_chromevox_next == '1' %}
   "automation": {
     "desktop": true
   },
   "commands": {
     "nextElement": {
       "description": "__MSG_CHROMEVOX_NEXT_OBJECT__",
       "suggested_key": {
         "chromeos": "Search+Right"
       }
     },
@@ skipping 81 matching lines @@
         "chromeos": "Search+Space"
       }
     },
     "toggleChromeVoxVersion": {
       "description": "__MSG_CHROMEVOX_TOGGLE_CHROMEVOX__",
       "suggested_key": {
         "chromeos": "Search+Ctrl+Q"
       }
     }
   },
-{% endif %}
   "options_page": "chromevox/background/options.html",
   "default_locale": "en"
 }