HarmonyOS WaterFlow组件使用sections进行布局，删除某一项之后布局计算异常

排查删除item时有没有sections.update，参考示例如下：

let index = this.dataSource.getIndexOfData(item);
this.dataSource.deleteItem(index);
this.oneColumnSection.itemsCount = this.oneColumnSection.itemsCount - 1;
this.sections.update(0, this.oneColumnSection)

问题根因WaterflowSections实例必须使用@State修饰，否则WaterflowSections update不会触发UI更新。将WaterflowSections实例定义在ViewModel中，规避方案：

private pageModal: PageModal = new PageModal();
@State sections: WaterFlowSections = this.pageModal.sections; // 从PageModal中取出sections，并用@State修饰