If you're simply looking to hide this route in the Help page and not actually disable it in the app, you could always tweak the logic in the display template.
You could modify the "...\DisplayTemplates\ApiGroup.cshtml" file by adding logic to look at each api that's going to be rendered and decide whether or not you want to include it based on the presence of a query string in the URL.
Still, the important thing to note is that this does not disable the route. You're just hiding it on this Help page. If you want to disable the route, I think you'll need to define your own custom routes.