[css-fonts] [palettes] Remove the none value from font-palette

Fixes w3c#6622.

Author: litherum

css-fonts-4/Overview.bs

@@ -6238,7 +6238,7 @@ as well as the colored versions.
 
 <pre class="propdef">
 Name: font-palette
-Value: none | normal | light | dark | <<palette-identifier>>
+Value: normal | light | dark | <<palette-identifier>>
 Initial: normal
 Applies to: all elements and text
 Inherited: yes
@@ -6248,12 +6248,6 @@ Animation type: discrete
 </pre>
 
 <dl dfn-for=font-palette dfn-type=value>
-	<dt><dfn>none</dfn></dt>
-	<dd>
-		User-Agents ignore colored (SVG or COLR) glyphs
-		and instead use the corresponding uncolored glyphs.
-	</dd>
-
 	<dt><dfn>normal</dfn>
 	<dd>
 		User-Agents attempt to treat the color font