To remove the pairing between a Macintosh and an iDevice you can delete the contents of /private/var/db/lockdown on the Mac. This is where the pairing certificates are stored. Following this action you’ll need to confirm on both the Mac and unlocked iDevice that they trust each other before any further syncing or data transfer will take place. Clearing out the pairing certificates will also prevent any automatic photo transfers when you plug in the iDevice to USB.
If you carry a paired Mac and iDevice together you can clear out the pairing certificates before setting off on your travels. This way if a bad actor gains access to the computer they won’t be able to affect a sync and hence pull data from the iDevice.
There’s no reason not to clear out this folder when in doubt since re-pairing is so easy - just a click and tap when prompted.