refactor(接口测试): 优化csv预览功能

--bug=1011052 --user=赵勇 【易保，企业客户】场景变量CSV，相关问题汇总 https://www.tapd.cn/55049933/s/1117938

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

@@ -125,7 +125,7 @@
         this.loading = false;
       },
       step(results, parser) {
-        if(this.allData.length < 2000) {
+        if(this.allData.length < 500) {
           this.allData.push(results.data);
         }else{
           this.showMessage = true;

frontend/src/i18n/en-US.js

@@ -2603,7 +2603,7 @@ export default {
   },
   variables: {
     ƒ: "Only CSV files can be uploaded",
-    csv_message: "2000 items are displayed by default, and the complete content can be downloaded and viewed.",
+    csv_message: "500 items are displayed by default, and the complete content can be downloaded and viewed.",
     end: "end",
     start: "start",
     increment: "increment",

frontend/src/i18n/zh-CN.js

@@ -2606,7 +2606,7 @@ export default {
   },
   variables: {
     cvs_info: "只能上传CSV文件",
-    csv_message: "默认展示2000条，完整的内容可点击下载查看。",
+    csv_message: "默认展示500条，完整的内容可点击下载查看。",
     end: "结束",
     start: "开始",
     increment: "增量",

frontend/src/i18n/zh-TW.js

@@ -2605,7 +2605,7 @@ export default {
   },
   variables: {
     cvs_info: "只能上傳CSV文件",
-    csv_message: "默認展示2000條，完整的內容可點擊下載查看。",
+    csv_message: "默認展示500條，完整的內容可點擊下載查看。",
     end: "結束",
     start: "開始",
     increment: "增量",