[css-containment] bikeshed fixups

Author: tabatkins

css-containment/Overview.bs

@@ -9,7 +9,7 @@ ED: http://dev.w3.org/csswg/css-containment/
 Editor: Tab Atkins, Google, http://xanthir.com/contact/
 Abstract: This CSS module describes the 'contain' property, which indicates that the element's subtree is independent of the rest of the page. This enables heavy optimizations by user agents when used well.
 Ignored Terms: scrollWidth, scrollHeight, clientWidth, clientHeight, formatting context
-Link Defaults: css-lists-3 (property) counter-increment
+Link Defaults: css-lists-3 (property) counter-increment, css-content-3 (property) string-set
 </pre>
 
 <h2 id='intro'>
@@ -123,7 +123,6 @@ Strong Containment: the 'contain' property</h2>
 
 			<ul>
 				<li>'break-*' (and the related aliases)
-				<li>'page-group'
 				<li>'bookmark-*'
 				<li>'string-set'
 			</ul>