[css-transitions-1] Align with Web IDL specification

Author: autokagami

css-transitions-1/Overview.bs

@@ -1085,9 +1085,9 @@ associated with transitions.
 ### IDL Definition ### {#interface-transitionevent-idl}
 
 <pre class="idl">
-  [Exposed=Window,
-   Constructor(CSSOMString type, optional TransitionEventInit transitionEventInitDict = {})]
+  [Exposed=Window]
   interface TransitionEvent : Event {
+    constructor(CSSOMString type, optional TransitionEventInit transitionEventInitDict = {});
     readonly attribute CSSOMString propertyName;
     readonly attribute double elapsedTime;
     readonly attribute CSSOMString pseudoElement;