[scroll-animations-1] Align with Web IDL specification (constructor)

Author: autokagami

scroll-animations-1/Overview.bs

@@ -375,9 +375,9 @@ dictionary ScrollTimelineOptions {
   (double or ScrollTimelineAutoKeyword) timeRange = "auto";
 };
 
-[Exposed=Window,
- Constructor(optional ScrollTimelineOptions options = {})]
+[Exposed=Window]
 interface ScrollTimeline : AnimationTimeline {
+  constructor(optional ScrollTimelineOptions options = {});
   readonly attribute Element scrollSource;
   readonly attribute ScrollDirection orientation;
   readonly attribute DOMString startScrollOffset;