Almost any bit long enough will work, as you really only need to take a millimeter or so off and you are cutting with the grain. If you have a sharp hand plane and can turn the top on its side it takes less time than setting up a router.
The question is how much you want to spend for a 1 3/4 inch long bit which can get expensive. I like flush trim bits with the bearing on the top. While you don't need a bearing, they come in handy later if you want to use a pattern (curves etc.) on some 2x stock. I would definitely go with a 1/2" over a 1/4" shank and a down spiral if you are partial to those rather than a traditional straight bit which is cheaper.
Tim