[css-overflow] delete stray text in example

Author: frivoal

css-overflow-4/Overview.bs

@@ -1904,7 +1904,7 @@ The new values of this property have the following meaning:
 					This situation poses no particular problem.">
 		</figure>
 		<figure>
-			<figcaption>Checkboxes and an overlay scrollbar classic scrollbar</figcaption>
+			<figcaption>Checkboxes and an overlay scrollbar</figcaption>
 			<img
 				src=images/todo-overlay.png
 				alt="