[css-color-4] comment out dangling color-mod reference in changes

Author: svgeesus

css-color-4/Overview.bs

@@ -3337,7 +3337,7 @@ Changes from Colors 3</h3>
 
 		<li>''hwb()'' function, for specifying colors in the HWB notation.
 
-		<li>''color-mod()'' function, for manipulating colors.
+		<!-- <li>''color-mod()'' function, for manipulating colors. -->
 
 		<li>''lab()'' and ''lch()'' functions, for device-independent color