[css-color-5] Remove leftover mention of gamut mapping to HSL w3c#8444

Author: svgeesus

css-color-5/Overview.bs

@@ -240,11 +240,6 @@ Mixing Colors: the ''color-mix()'' Function {#color-mix}
 After normalizing both percentages, the result is produced via the following algorithm:
 
 1. Both colors are converted to the specified <<color-space>>.
-	If the specified color space
-	cannot express the color
-	(for example, the ''hsl'' and ''hwb'' spaces
-	cannot express colors outside the ''sRGB'' gamut),
-	gamut mapping will occur.
 2. Colors are then interpolated in the 	specified color space,
 	as described in [[css-color-4#interpolation]].
 	If the specified color space is a ''cylindrical-polar-color'' space,