nixos: k0: temporarily disable 4th monitor
nixos: k0: temporarily disable 4th monitor

The 4th monitor has died (CCFL backlight lamp failure); the cost to buy
a replacement lamp is absurd, along with the fact that actually
replacing the lamp and putting the monitor back together into one piece
is a serious challenge.

listx/syscfg,listx/syscfg,listx/syscfg,listx/syscfg,listx/syscfg