Under the location "Settings -> Add devices by IP -> Custom device list" to manually specify an IP address in the event autodiscover is not working properly it is opaque how one is supposed to remove an entry should it be no longer needed.

The action that needs to be taken is to swipe left or right on the entry, but in my experience this is a very rare interaction in apps so it took me a while to think of trying it. The only other apps I know of that employ swiping are email apps, and even then they provide an alternate method of long-pressing.