fix a typo in the docs (#1203)
fix a typo in the docs (#1203)


microsoft/LightGBM,microsoft/LightGBM,Laurae2/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,Laurae2/LightGBM,henry0312/LightGBM,henry0312/LightGBM,Laurae2/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,Laurae2/LightGBM