Remove empty module (#2558)

self explanatory

Author: BoxyUwU

crates/bevy_ecs/src/world/mod.rs

@@ -1,10 +1,9 @@
 mod entity_ref;
-mod pointer;
 mod spawn_batch;
 mod world_cell;
 
+pub use crate::change_detection::Mut;
 pub use entity_ref::*;
-pub use pointer::*;
 pub use spawn_batch::*;
 pub use world_cell::*;