vote_up_down callback should be not in $may_cache section

Hello

Recently I have worked on site with a lot of modules that are changing user roles dinamically. So, users can gain rights to vote on site, but sometimes they cant because of 403 error on javascript callback of vote_up_down. The reason of it - caching the access to menu callback of vote_updown. When I moved callback to "not cache" sections all becomes fine.

I attached the patch to help you solve this issue quickly.