That's kind of bass ackwards. You tighten the top cap to get the right preload, then tighten (using a torque wrench) the stem bolts. I'd leave the cap setting as is. Removing it exposes the threads to the elements and leaves the possibly rough edge of the fork tube exposed.

There is no advantage in tightening the cap once the stem bolts are in place.

There are minimal advantages and some significant disadvantages to removing the cap.

But aggiegrads asked the right question: what do you hope to accomplish by tightening the cap screw?