remove unused import

Author: jakobhellermann

crates/bevy_ecs/src/change_detection.rs

@@ -781,8 +781,6 @@ impl std::fmt::Debug for MutUntyped<'_> {
 
 #[cfg(test)]
 mod tests {
-    use std::ptr::NonNull;
-
     use bevy_ecs_macros::Resource;
     use bevy_ptr::PtrMut;
     use bevy_reflect::{FromType, ReflectFromPtr};