[css-color-4] Correct section title to account for updated contents

Author: svgeesus

css-color-4/Overview.bs

@@ -1908,7 +1908,7 @@ Profiled, Device-dependent Colors</h2>
 	''color()'' represents <a>opaque black</a>.
 
 <h3 id="predefined">
-Predefined colorspaces: ''srgb'', ''image-p3'', and ''rec2020''.</h3>
+Predefined colorspaces: ''srgb'', ''image-p3'', ''a98rgb'', ''prophotorgb'' and ''rec2020''.</h3>
 
 	The following colorspaces are predefined for use in the ''color()'' function.
 	They can be used without any ''@color-profile'' rule.