[css-color-5] at least two colors for color-contrast() list. Fix w3c#6055

Author: svgeesus

css-color-5/Overview.bs

@@ -504,7 +504,7 @@ Selecting the most contrasting color: the ''color-contrast()'' function {#colorc
 	to the single color.
 
 	<pre class='prod'>
-		<dfn>color-contrast()</dfn> = color-contrast( <<color>> vs <<color>>#  )
+		<dfn>color-contrast()</dfn> = color-contrast( <<color>> vs <<color>>#{2,}  )
 	</pre>
 
 	Issue(#4749): <a href="https://github.com/w3c/csswg-drafts/issues/4749">add target contrast ratio to color-contrast?</a>