[R-package] fix typo in linear learner test (#4109)
[R-package] fix typo in linear learner test (#4109)


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