[R-package] allow for small numerical differences in Booster test (#4714)
[R-package] allow for small numerical differences in Booster test (#4714)

* [R-package] allow for small numerical differences in Booster test

* only use less-strict test on Windows
henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM