[css-align] Remove extraneous wording

Author: fantasai

css-align/Overview.bs

@@ -805,7 +805,7 @@ Block/Cross-Axis Alignment: the 'align-self' property</h3>
 	The <dfn value for="align-self">auto</dfn> keyword computes to
 	itself on absolutely-positioned elements,
 	and to the computed value of 'align-items' on the parent
-	(minus any ''legacy'' keywords) on all other boxes,
+	on all other boxes,
 	or ''align-self/start'' if the box has no parent.
 	Its behavior depends on the layout model, as described for 'justify-self'.