[docs] Improve some phrasing in the installation guide (#3214)
[docs] Improve some phrasing in the installation guide (#3214)

* Improve some phrasing

* implement requested changes
henry0312/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM