[css-display] Use the right terms when referring to list-items. Fixes #1226.

Author: tabatkins

css-display/Overview.bs

@@ -378,9 +378,9 @@ Generating Marker Boxes: the ''list-item'' keyword</h3>
 	(<a href="https://www.w3.org/TR/CSS2/generate.html#lists">CSS 2.1§12.5 Lists</a>) [[!CSS2]]
 	together with a principal box of the specified type for its own contents.
 
-	If no <<display-inside>> value is specified,
+	If no <a>inner display type</a> value is specified,
 	the principal box's <a>inner display type</a> defaults to ''flow''.
-	If no <<display-outside>> value is specified,
+	If no <a>outer display type</a> value is specified,
 	the principal box's <a>outer display type</a> defaults to ''block''.
 
 	Note: In this level, as restricted in the grammar,