[css-ui] Tweaks to implementation report

Author: frivoal

css-ui-3/implementation-report.html

@@ -2228,7 +2228,7 @@ <h2 id=license><a href="#license" class=self-link></a>License</h2>
 <h2 id=ack><a href="#ack" class=self-link></a>Acknowledgements</h2>
 
 <p>Many thanks to the following for their contributions:
-<ul>
+<ul class=short-list>
 	<li>Chris Lilley
 	<li>Chris Rebert
 	<li>Elika J. Etemad