[docs][R-package] change obsolete wordings in R README (#3728)
[docs][R-package] change obsolete wordings in R README (#3728)


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