[Datasets] Remove the non-useful comment in map_batches() (ray-proj…

…ect#32020)

This PR is a quick fix to remove the non-useful comment introduced in ray-project#31526, probably during debugging.

Replace the comment with a meaningful one.

Signed-off-by: Edward Oakes <ed.nmi.oakes@gmail.com>

python/ray/data/dataset.py

@@ -614,7 +614,7 @@ def map_batches(
             zero_copy_batch=zero_copy_batch,
         )
 
-        # breakpoint()
+        # TODO(chengsu): pass function name to MapBatches logical operator.
         if hasattr(fn, "__self__") and isinstance(
             fn.__self__, ray.data.preprocessor.Preprocessor
         ):