fix index and remove unused includes (#2829)

* removed unused includes

* fixed index

src/boosting/gbdt.cpp

@@ -10,7 +10,6 @@
 #include <LightGBM/prediction_early_stop.h>
 #include <LightGBM/utils/common.h>
 #include <LightGBM/utils/openmp_wrapper.h>
-#include <LightGBM/utils/threading.h>
 
 #include <chrono>
 #include <ctime>

src/boosting/goss.hpp

@@ -8,7 +8,6 @@
 #include <LightGBM/boosting.h>
 #include <LightGBM/utils/array_args.h>
 #include <LightGBM/utils/log.h>
-#include <LightGBM/utils/openmp_wrapper.h>
 
 #include <string>
 #include <algorithm>

src/treelearner/feature_histogram.hpp

@@ -595,7 +595,7 @@ class FeatureHistogram {
 
         double sum_left_gradient = sum_gradient - sum_right_gradient;
         if (IS_RAND) {
-          if (t + offset != rand_threshold) {
+          if (t - 1 + offset != rand_threshold) {
             continue;
           }
         }