Method deleteUnused

pj_plotting/widget/src/PlotDocker.cpp:257–263

  }

  void deleteUnused() {
    for (PlotWidget* plot : plots_by_position_) {
      if (plot != nullptr && !used_.contains(plot)) {
        plot->deleteLater();
      }
    }
  }

 private:
  PlotWidget* createPlot(const QString& state_id) {