Default to the second vpart in veh_interact remove

This is a quality-of-life improvement for when removing large numbers of vehicle parts. The part removal menu lists all the vehicle parts in the current tile with the frame first, but that frame is almost always the last thing that can be removed from the current tile. Therefore, if more than one part is present, we will select the second part instead.

Note that parts with attachments (e.g. alternators on engines, or seatbelts on seats) are actually listed in the correct order for this to continue working (i.e. seatbelts come first, then the seat they're attached to).