Remove Scrollbar on Custom CSS editor

[acketon]

The custom css editor has a scrollbar appear if you have more than about 50 lines of code it looks like. This is unnecessary as the page itself has a scrollbar and you end up having to scroll both to find a line of css.

The editor box should just expand as needed and utilize the scrollbar of the page so that a user does not have to scroll both locations to make an edit.