Unfortunately, there is no way that I know of to remove a single device from your trusted device list. For some reason, Microsoft has made it so that to remove one device, you have to remove ALL devices. So, you will need to go to the Microsoft Account Page (account.live.com) and then go to “Security and password” settings. Once there, go down to the “trusted devices” section and click on “remove all the trusted devices associated with my account.”
The obvious downside of this is that you are going to have to go back and add all of your previously trusted devices to the trusted device list again. Hopefully Microsoft will change this in a future update so that you can easily remove a single device.