Taking from an internal report % private stuff.

It's reported that updating an extension to have the "incognito": "not_allowed" entry in the manifest doesn't update the existing preferences for users who may have already allowed it incognito, and isn't shown properly in the settings.

If an extension adds the incognito: not_allowed setting, we should be sure that the chrome://extensions page displays the extension info correctly.  We *may* also want to clear the preference for the extension; however, that would mean the extension wouldn't retain the permission if it was added back at a later point.