fix(测试跟踪)：功能用例关联的devops需求，保存后回显为空

--bug=1022341 --user=王旭 【测试跟踪】github#21508，功能用例关联的devops需求，保存后回显为空 https://www.tapd.cn/55049933/s/1347263

test-track/frontend/src/business/case/components/case/CaseBaseInfo.vue

@@ -702,7 +702,6 @@ export default {
       this.result = { loading: false };
     },
     buildDemandCascaderOptions(data, options, pathArray) {
-      this.demandValue = [];
       data.forEach((item) => {
         let option = {
           label: item.platform + ": " + item.name,