fix(接口测试): 修复mock面板点击请求体变量没反应的问题

--bug=1017952 --user=宋天阳 【接口测试】mock - 后置脚本，点击 “请求体变量” 模板没有反应
https://www.tapd.cn/55049933/s/1260581

api-test/frontend/src/business/automation/scenario/testplan/TestPlanList.vue

@@ -4,8 +4,7 @@
       <ms-table-header :condition.sync="condition"
                        @search="initTableData"
                        :title="$t('test_track.plan.test_plan')"
-                       @create="testPlanCreate"
+                       :show-create="false"
-                       :create-tip="$t('test_track.plan.create_plan')"
       >
       </ms-table-header>
     </template>

api-test/frontend/src/business/definition/components/mock/Components/MockApiScriptEditor.vue

@@ -194,6 +194,8 @@ export default {
         case "body":
           if (laguanges === "python") {
             returnScript = 'param=vars["body.${param}"]';
+          } else {
+            returnScript = 'var param=vars.get("body.${param}")';
           }
           break;
         case "bodyRaw":