[css-align] Link to the correct term.

Author: tabatkins

css-align/Overview.bs

@@ -710,7 +710,7 @@ Overflow and Scroll Positions</h3>
 	The <a>content distribution properties</a> also affect the initial scroll position,
 	setting it to display the appropriate portion of the scrollable area.
 	In other words,
-	the scrollable area is aligned relative to the viewport
+	the <a>scrollable overflow region</a> is aligned relative to the viewport
 	as specified by the <a>content distribution property</a>.
 
 	<div class='example'>