If it were me, I would just keep it and leave it disabled. It would just be a good reminder that that's the physical port. I would also probably name my VLAN interfaces LAN-V101, LAN-V102, etc… so you include the name of the physical interface with the VLAN number. This might not be a big deal if you only have two physical interfaces (WAN and LAN), but if you had three or four physical interfaces and multiple VLANs on each, that might help to keep things straight.