[css-scrollbar] Fix typo

see #10591

css-scrollbars-1/Overview.bs

@@ -294,7 +294,7 @@ Value Definitions</h3>
 	in order to visually respond to user interactions with the scrollbar
 	(e.g. hovering or activating):
 	they could alter which scrollbar parts the specified colors apply to,
-	using darker or lighter shades of the specified colors,
+	use darker or lighter shades of the specified colors,
 	more or less saturated variants…
 
 	If the user agent displays the scrollbar without the [=track=],