[Cupertino] Hero fix

Runtime/widgets/heroes.cs

             HeroFlightShuttleBuilder shuttleBuilder,
             bool isUserGestureTransition
         ) {
-            D.assert(fromHero.widget.tag.ToString() == toHero.widget.tag.ToString());
+            D.assert(fromHero.widget.tag.Equals(toHero.widget.tag));
             this.type = type;
             this.overlay = overlay;
             this.navigatorRect = navigatorRect;