message: Update iterator-for-combination.cpp
diff: @@ -12,7 +12,7 @@ public:
  }
  string next() {
  - iterative_dfs();
  + iterative_backtracking();
  return curr_;
  }
  @@ -21,7 +21,7 @@ public:
  }
  private:
  - void iterative_dfs() {
  + void iterative_backtracking() {
  while (!stk_.empty()) {
  const auto cb = move(stk_.back());
  stk_.pop_back();
  