[css-ui-3] Don't call it a working draft, it isn't

Part of w3c#3062

Author: frivoal

css-ui-3/Overview.bs

@@ -104,7 +104,7 @@ and <a href="https://www.w3.org/TR/CSS2/ui.html">Chapter 18 of CSS2</a> [[CSS2]]
 introduced several user interface related properties and values.
 <a href="https://www.w3.org/TR/2000/WD-css3-userint-20000216">User Interface for CSS3 (16 February 2000)</a> introduced several new user interface related features.
 
-This Working Draft incorporates, extends, and supersedes them.
+This specification incorporates, extends, and supersedes them.
 
 <h3 id="purpose">Purpose</h3>