Either will probably work, just stop the witness service on the arrays, either remove the existing witness and create new one pointing at the new IP or rebuild/move with the old IP and start the witness service again.
We tend to build a new one for new witness version on a new IP and then stop/remove/create/start on the arrays to point at it. Just takes a minute or two to settle.
Below are the commands from my reminder notes.
Code:
setrcopytarget witness check <IP of Quorum Witness>
setrcopytarget witness create <IP of Quorum Witness> <target_name>
showrcopy -qw targets
setrcopytarget witness start <target_name>
setrcopytarget witness start –remote <target_name>
setrcopytarget witness stop <target_name>
setrcopytarget witness remove <target_name>