Override header CSS changes in 4chan X v1.9.7.0.

Not sure if this is the right place in the code or preferred method to do this, but I made some changes to the CSS of the header in 4chan X v1.9.7.0 which you probably want to override since it messes up the position of the full board list with OneeChan on.  Specifically, I've added `vertical-align: middle` to the `#custom-board-list`, `#full-board-list`, and `.shortcut` selectors.