[css-lists-3] Improve Abstract.

Author: tabatkins

css-lists-3/Overview.bs

@@ -17,7 +17,7 @@ Previous Version: https://www.w3.org/TR/2011/WD-css3-lists-20110524/
 !Contributors: Daniel Yacob, <a href="mailto:yacob@geez.org">yacob@geez.org</a>
 !Contributors: Christopher Hoess, <a href="mailto:choess@stwing.upenn.edu">choess@stwing.upenn.edu</a>
 !Contributors: Daniel Glazman, AOL-TW/Netscape, <a href="mailto:glazman@netscape.com">glazman@netscape.com</a>
-Abstract: This draft contains the features of CSS level&nbsp;3 relating to list styling. It includes and extends the functionality of CSS level&nbsp;2 [[!CSS21]]. The main extensions compared to level&nbsp;2 are a pseudo-element representing the list marker, and some new ways to position markers.
+Abstract: This module contains CSS features related to list counters: styling them, positioning them, and manipulating their value.
 </pre>
 
 <pre class='link-defaults'>