Fix bad JS rendering in "Allow Desktop Notifications" workflow

Summary:
See downstream https://phabricator.kde.org/T5404. This code was doing some .firstChild shenanigans which didn't survive some UI refactoring.

This whole UI is a little iffy but just unbreak it for now.

Test Plan: Allowed and rejected desktop notifications, got largely reasonable UI rendering.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D17388