Fix Alien Cake Addict example despawn warnings (#7236)

# Problem
The example's `teardown` system despawns all entities besides the camera using `despawn_recursive` causing it to despawn child entities multiple times which logs a warning.
![image](https://user-images.githubusercontent.com/29694403/212756554-06b3fa42-ddcb-4a05-b841-f587488a10fc.png)

# Solution
Use `despawn` instead.

Co-authored-by: Devil Ira <[email protected]>

examples/games/alien_cake_addict.rs

@@ -179,7 +179,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>, mut game: ResMu
 // remove all entities that are not a camera
 fn teardown(mut commands: Commands, entities: Query<Entity, Without<Camera>>) {
     for entity in &entities {
-        commands.entity(entity).despawn_recursive();
+        commands.entity(entity).despawn();
     }
 }