[css-fonts-4] CSSFontPaletteValuesRule.overrideColor needs to be plural

It needs to be updated after w3c@09ddc0c

Author: litherum

css-fonts-4/Overview.bs

@@ -6881,7 +6881,7 @@ interface CSSFontPaletteValuesRule : CSSRule {
   readonly attribute CSSOMString name;
   readonly attribute CSSOMString fontFamily;
   readonly attribute CSSOMString basePalette;
-  readonly attribute CSSOMString overrideColor;
+  readonly attribute CSSOMString overrideColors;
 };</pre>
 
 The <code>fontFamily</code> and <code>basePalette</code> interfaces are parsed according to the appropriate CSS property syntax.