[bp/r47346][FIX] tabcontent z-index was too high (there's no need to specify this in a theme stylesheet in any case). Good catch by Pete and Jonny.

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/9.x@47348 b456876b-0849-0410-b77d-98878d47e9d5