Remove device when no longer in possession
I swapped devices with a friend a few months back. Now I'm getting a message that it couldn't be connected with because of being locked with a passcode. When I look in iTunes I'm running into the 10 device limit based on number of devices I've had (and didn't know I needed to remove).
The problem is that all are greyed out with the exception of one (the PC I'm writing this on) and I don't want to erase someone else's data by doing an erasure.
How do I remove what I don't need?
iPad Air Wi-Fi, iOS 11, Old device that was swapped