If you use blink and need to remove a known_host due to a fingerprint change it’s a bit hidden. When you launch blink you’ll see the bare bones shell with the prompt what you need to do is treat it like an actual Unix system. There is a .ssh/known_hosts file. You won’t have vi or any other editor available as far as I can tell, but you can remove the file and create a new connection to your reused host.
blink> rm -rf ~/.ssh/known_hosts