fix reflect feature gate (#20811)

# Objective

- fix building bevy_window with reflect disabled

## Solution

- I missed one last thing to gate last time I tried to fix it

## Testing

`cargo build -p bevy_window --no-default-features --features
bevy_math/libm`

Author: mockersf

crates/bevy_window/src/cursor/mod.rs

@@ -8,7 +8,9 @@ mod system_cursor;
 pub use custom_cursor::*;
 pub use system_cursor::*;
 
-use bevy_ecs::{component::Component, reflect::ReflectComponent};
+use bevy_ecs::component::Component;
+#[cfg(feature = "bevy_reflect")]
+use bevy_ecs::reflect::ReflectComponent;
 #[cfg(feature = "bevy_reflect")]
 use bevy_reflect::{std_traits::ReflectDefault, Reflect};