Still not fixed, just can't believe it.
Use the Contact Us link below, request a phone call, during which you should explain that you want devices removed in order to continue testing via Xcode Free Provisioning, and ask them to remove devices. They will take a look, confirm which one(s) you want dropped and after a wait for the info to update on the backend, you can go about your business.
But if you're insisting on a change to the limit, keep in mind that free provisioning is just so individuals can toe-dip the tools/IDE - it is only by the grace of Apple that it's even allowed, as in no free lunch. More devices is 'fixed' by purchasing an account. Seems fair, after all.
Good luck.