[docs] [dask] Add return information to Dask fit() docs (fixes #4402) (#4716)
[docs] [dask] Add return information to Dask fit() docs (fixes #4402) (#4716)

* [docs] [dask] Add return information to Dask fit() docs (fixes #4402)

* put return before note
henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM