Fix meshlet private item regression (#16404)

I didn't mean to make this item private, fixing it for the 0.15 release
to be consistent with 0.14.

(maintainers: please make sure this gets merged into the 0.15 release
branch as well as main)

Author: JMS55

crates/bevy_pbr/src/meshlet/mod.rs

@@ -33,7 +33,9 @@ pub(crate) use self::{
     },
 };
 
-pub use self::asset::{MeshletMesh, MeshletMeshLoader, MeshletMeshSaver};
+pub use self::asset::{
+    MeshletMesh, MeshletMeshLoader, MeshletMeshSaver, MESHLET_MESH_ASSET_VERSION,
+};
 #[cfg(feature = "meshlet_processor")]
 pub use self::from_mesh::{
     MeshToMeshletMeshConversionError, MESHLET_DEFAULT_VERTEX_POSITION_QUANTIZATION_FACTOR,