fix(接口测试): 修复修改body参数，不弹同步框的缺陷

--bug=1025768 --user=王孝刚
【接口测试】api增加请求参数-保存-关闭一键同步弹框-删除增加参数-修改历史参数值-保存没反应
https://www.tapd.cn/55049933/s/1366281

api-test/frontend/src/business/definition/components/complete/EditCompleteHTTPApi.vue

@@ -674,7 +674,7 @@ export default {
                       ordered[key] = newRequest[key];
                     });
                   requestKvs.push(ordered);
-                  let beforeRequest = this.request.body.kvs[i];
+                  let beforeRequest = this.beforeRequest.body.kvs[i];
                   const beforeOrdered = {};
                   Object.keys(beforeRequest)
                     .sort()