Update multi_asset_sync.rs (#15816)

Typo

examples/asset/multi_asset_sync.rs

@@ -59,7 +59,7 @@ pub struct OneHundredThings([Handle<Gltf>; 100]);
 ///
 /// For sync only the easiest implementation is
 /// [`Arc<()>`] and use [`Arc::strong_count`] for completion.
-/// [`Arc<Atomic*>`] is a more robust alternative.
+/// [`Arc<Atomic>`] is a more robust alternative.
 #[derive(Debug, Resource, Deref)]
 pub struct AssetBarrier(Arc<AssetBarrierInner>);