Remove hexDigit check in CSSParserValueList

LayoutTests/fast/css/script-tests/invalid-predefined-color.js

 description(
 "This test checks hexadecimal color parsing."
 );
 
 var red = "rgb(255, 0, 0)";
 var black = "rgb(0, 0, 0)";
 
 for (var i=1;i<=5;i++)
 {
     var div = document.getElementById("valid"+i);
     shouldBe("getComputedStyle(div, null).color", "red");
 }
 
-for (var i=1;i<=5;i++)
+for (var i=1;i<=6;i++)
 {
     var div = document.getElementById("invalid"+i);
     shouldBe("getComputedStyle(div, null).color", "black");
 }