Change error code for invalid KeyfameEffect pseudo-selector to SyntaxError (w3c#4829)

Author: george-steel

web-animations-1/Overview.bs

@@ -4846,7 +4846,7 @@ interface KeyframeEffect : AnimationEffect {
 
     *   If the provided value is not `null` or a syntactically valid
         <<pseudo-element-selector>> the user agent must [=throw=]
-        a {{DOMException}} with error name {{TypeError}} and leave the
+        a {{DOMException}} with error name {{SyntaxError}} and leave the
         [=target pseudo-selector=] of this [=animation effect=] unchanged.
 
     *   If one of the legacy Selectors Level 2 single-colon selectors