correct return type hint

Author: TomNicholas

src/zarr/core/indexing.py

@@ -964,7 +964,7 @@ def __setitem__(self, selection: OrthogonalSelection, value: npt.ArrayLike) -> N
 class AsyncOIndex:
     array: AsyncArray
 
-    async def getitem(self, selection: OrthogonalSelection | Array) -> NDArrayLike:
+    async def getitem(self, selection: OrthogonalSelection | Array) -> NDArrayLikeOrScalar:
         from zarr.core.array import Array
 
         # if input is a Zarr array, we materialize it now.