remove outdated comment

pandas/core/frame.py

@@ -8651,7 +8651,6 @@ def blk_func(values):
  res = df._mgr.reduce(blk_func)
  out = df._constructor(res,).iloc[0].rename(None)
  if out_dtype is not None:
- # only astype if result is empty
  out = out.astype(out_dtype)
  if axis == 0 and is_object_dtype(out.dtype):
  out[:] = coerce_to_dtypes(out.values, df.dtypes)