It's only a little dribble, working it's way round the threads of the drive unit, but obviously a little drip can go a long way, (just look at Tony Blair), so if you're not using it, then definitely blank it off. I found cutting the screw-on fitting from the end of an old Reliant cable & blanking the hole in it with a rubber blanking grommet, sealed with a dab of Araldite glue, did the job on my last one.
Alternatively, give Twisted Patience or FLC a shout & persuade them to machine you a purpose made blanking cap.