use std::greater instead of custom predicate (ydb-platform#15227)

Author: zverevgeny

ydb/core/tx/columnshard/engines/storage/optimizer/lcbuckets/planner/optimizer.h

@@ -13,13 +13,7 @@ class TOptimizerPlanner: public IOptimizerPlanner {
     std::shared_ptr<TSimplePortionsGroupInfo> PortionsInfo = std::make_shared<TSimplePortionsGroupInfo>();
 
     std::vector<std::shared_ptr<IPortionsLevel>> Levels;
-    class TReverseSorting {
-    public:
-        bool operator()(const ui64 l, const ui64 r) const {
-            return r < l;
-        }
-    };
-    std::map<ui64, std::shared_ptr<IPortionsLevel>, TReverseSorting> LevelsByWeight;
+    std::map<ui64, std::shared_ptr<IPortionsLevel>, std::greater<ui64>> LevelsByWeight;
     const std::shared_ptr<IStoragesManager> StoragesManager;
     const std::shared_ptr<arrow::Schema> PrimaryKeysSchema;
     virtual std::vector<TTaskDescription> DoGetTasksDescription() const override {