The official way to uninstall ACR is to uninstall Photoshop or whatever Adobe product ACR came with.
If you have not been offered the non-beta ACR since the first of August when it was first available then there is something wrong with what is tracking the versions of things and an uninstaller would not necessarily help with that. I mean, even if there was an uninstaller, you might uninstall ACR 8.6 RC and still not be offered any update and be stuck without any ACR. So the ultimate solution is to reset things enough that the Adobe version database and processes to make everything work like it should, again. I’m not sure exactly how to do this. On way is to uninstall all Adobe products then run the CC Cleaner and then reinstall all Adobe products.
Without fixing the underlying issue, it might also should work to use the manual installers you can download from an Adobe HELPX page with direct links:
http://helpx.adobe.com/x-productkb/multi/camera-raw-plug-in-installer.html