[css-images-3] bikeshed fixes

Author: tabatkins

css-images-3/Overview.bs

@@ -1009,7 +1009,7 @@ Gradient Color-Stops {#color-stop-syntax}
 
 	<pre class=prod>
 		<dfn>&lt;color-stop-list></dfn> = <<color-stop>>{2,}
-		<dfn>&lt;color-stop></dfn> = <color> [ <percentage> | <length> ]?
+		<dfn>&lt;color-stop></dfn> = <<color>> [ <<percentage>> | <<length>> ]?
 	</pre>
 
 	The colors in gradients are specified using <a>color stops</a>.