[css-color-4][editorial] remove commented-out reference to device-cmyk which no longer applies

Author: svgeesus

css-color-4/Overview.bs

@@ -516,8 +516,6 @@ Representing Colors: the <<color>> type</h2>
 		(or more, in the case of CMYK or CMYKOGV)
 		orthogonal component axes.
 
-	<!--  <<device-cmyk()>> does not actually specify a color; it can't be converted to Lab -->
-
 	For easy reference in other specifications,
 	<dfn export>opaque black</dfn> is defined as the color <nobr>''rgb(0 0 0 / 100%)''</nobr>;
 	<dfn export>transparent black</dfn> is the same color,