fix intro doco for UrgencyHook
fix intro doco for UrgencyHook

Ooh, this new XConfig l -> XConfig l' function makes the docs disappear!

mathstuf/xmonad-contrib,pjones/xmonad-test,CaptainPatate/xmonad-contrib,xmonad/xmonad-contrib,0/xmonad-contrib,xmonad/xmonad-contrib,ohlus/xmonad-contrib,mathstuf/xmonad-contrib,ohlus/xmonad-contrib,0/xmonad-contrib,CaptainPatate/xmonad-contrib,ohlus/xmonad-contrib,f1u77y/xmonad-contrib,CaptainPatate/xmonad-contrib,0/xmonad-contrib,f1u77y/xmonad-contrib,mathstuf/xmonad-contrib