[mediaqueries-5] Remove mention of prefers-color-scheme:no-preference

Author: tabatkins

css-color-adjust-1/Overview.bs

@@ -340,7 +340,7 @@ Forced Color Schemes: the 'forced-color-adjust' property {#forced}
 	Behavior between the above dark vs. light thresholds
 	is UA-defined,
 	and may result in assuming either
-	''prefers-color-scheme/light'', ''prefers-color-scheme/dark'', or ''prefers-color-scheme/no-preference''
+	''prefers-color-scheme/light'' or ''prefers-color-scheme/dark''
 	as the user’s preferred color scheme.
 
 <!--THOUGHTS