fix(场景案例): 修复场景变量编辑时自动生成变量的问题

--bug=1008067 --user=宋天阳 【接口测试】场景变量自动添加空的变量列
https://www.tapd.cn/55049933/s/1074274

frontend/src/business/components/api/automation/scenario/variable/VariableList.vue

@@ -272,8 +272,6 @@ export default {
         this.headers = headers;
       }
       this.visible = true;
-      this.editData = {type: "CONSTANT"};
-      this.addParameters(this.editData);
       this.disabled = disabled;
     },
     save() {