Rename Widget::on_event to update

widget/src/scrollable.rs

@@ -508,7 +508,7 @@ where
         );
     }
 
-    fn on_event(
+    fn update(
         &mut self,
         tree: &mut Tree,
         event: Event,
@@ -724,7 +724,7 @@ where
                 let translation =
                     state.translation(self.direction, bounds, content_bounds);
 
-                self.content.as_widget_mut().on_event(
+                self.content.as_widget_mut().update(
                     &mut tree.children[0],
                     event.clone(),
                     content,