config: whitelist option to hide chrome extension banner

saghul: torture tests also need it.

react/features/base/config/interfaceConfigWhitelist.js

     'RECENT_LIST_ENABLED',
     'REMOTE_THUMBNAIL_RATIO',
     'SETTINGS_SECTIONS',
+    'SHOW_CHROME_EXTENSION_BANNER',
     'SHOW_DEEP_LINKING_IMAGE',
     'SHOW_POWERED_BY',
     'SUPPORT_URL',