[css-scroll-snap] Fix problematic wording for overflowing scroll snap areas with overlapping snap positions.

Author: fantasai

css-scroll-snap/Overview.bs

@@ -636,7 +636,8 @@ Scoping Valid Snap Positions to Visible Boxes</h4>
 Snapping Boxes that Overflow the Scrollport</h4>
 
 	If the <a>snap area</a> is larger than the <a>scroll snapport</a> in a particular axis,
-	and there are no other <a>snap areas</a> within the <a>scroll snapport</a>,
+	and there are no other <a>snap areas</a> within the <a>scroll snapport</a>
+	that would provide a <a>snap position</a> aligning the overflowing <a>snap area</a> within the <a>snapport</a>,
 	then any scroll position in which the <a>snap area</a> covers the <a>scroll snapport</a>
 	is a valid <a>snap position</a> in that axis.
 	The UA may use the specified alignment as a more precise target