[dask] remove unused imports from typing (#4079)
[dask] remove unused imports from typing (#4079)


henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM