[css-cascade] Fix copy/paste error.

Author: fantasai

css-cascade-3/Overview.bs

@@ -2,11 +2,11 @@
 
 <pre class='metadata'>
 Shortname: css-cascade
-Level: 4
+Level: 3
 Status: ED
 Group: csswg
-ED: http://dev.w3.org/csswg/css-cascade/
-TR: http://www.w3.org/TR/css-cascade-4/
+ED: http://dev.w3.org/csswg/css-cascade-3/
+TR: http://www.w3.org/TR/css-cascade-3/
 Editor: fantasai, Mozilla, http://fantasai.inkedblade.net/contact
 Editor: Tab Atkins Jr., Google, http://xanthir.com/contact/
 Previous Version: http://www.w3.org/TR/2013/WD-css-cascade-3-20130730/