fix(接口测试): 修复复制的场景无法添加前后置操作的缺陷

--bug=1026590 --user=王孝刚 [接口测试]
github#24667最新版MS的接口自动化-场景导入-场景复制后，无法进行前后置脚本编写
https://www.tapd.cn/55049933/s/1377024

api-test/frontend/src/business/automation/scenario/component/ApiScenarioComponent.vue

@@ -300,7 +300,6 @@ export default {
         arr[i].disabled = disabled;
         arr[i].isCopy = false;
         arr[i].projectId = this.calcProjectId(arr[i].projectId, id);
-        arr[i].notAddStep = true;
         // 处理子请求环境
         let typeArray = ['JDBCPostProcessor', 'JDBCSampler', 'JDBCPreProcessor'];
         if (typeArray.indexOf(arr[i].type) !== -1) {

api-test/frontend/src/business/definition/components/step/JmxStep.vue

@@ -13,7 +13,6 @@
         @click="add"
         type="primary"
         v-if="tabType !== 'assertionsRule'"
-        :disabled="request.notAddStep"
         style="background-color: var(--primary_color); border-color: var(--primary_color)">
         {{ $t('api_test.request.assertions.add') }}
       </el-button>