[docs] Fix repetition of `tree_method` hyper-parameter in xgboost_hist experiment (#3296)
[docs] Fix repetition of `tree_method` hyper-parameter in xgboost_hist experiment (#3296)

Co-authored-by: Nikita Titov <31eaea17affb14e78210388fc0bace3c2fd52ddc@mail.ru>
henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM,henry0312/LightGBM,microsoft/LightGBM,henry0312/LightGBM,microsoft/LightGBM,microsoft/LightGBM,henry0312/LightGBM