Specs: fix copypasta in the WheelEvent constructor

sky/specs/pointer.md

Index: sky/specs/pointer.md
diff --git a/sky/specs/pointer.md b/sky/specs/pointer.md
index eaf17f27de6515b430c09cda45443779e245f07f..5001f3d5b6f4b21b15b0148707e9232978bfc216 100644
--- a/sky/specs/pointer.md
+++ b/sky/specs/pointer.md
@@ -471,12 +471,11 @@ dials. Track balls are not reported as mouse wheels.
 
 ```dart
 class WheelEvent extends Event {
-  PointerEvent({ bool bubbles,
-                 this.wheel,
-                 this.delta: 0.0,
-                 this.pointer,
-                 this.x, this.y,
-               }): super(bubbles: bubbles);
+  Event({ this.wheel,
+          this.delta: 0.0,
+          this.pointer,
+          this.x, this.y,
+        }): super();
 
   final int wheel;
   final double delta; // revolutions (or fractions thereof)