refactor(性能测试): 去掉上传文件最大数量限制

--bug=1018520 --user=刘瑞斌 【性能测试】github#18629，性能测试中文件上传有数量限制，删除文件后再上传还会提示超过数量限制 https://www.tapd.cn/55049933/s/1269205

Closes #18629

performance-test/frontend/src/business/test/components/ExistFiles.vue

@@ -12,7 +12,6 @@
           accept=".jmx"
           action=""
           multiple
-          :limit="fileNumLimit"
           :show-file-list="false"
           :before-upload="beforeUploadFile"
           :http-request="handleUpload"
@@ -27,7 +26,6 @@
           style="margin-bottom: 10px"
           accept=".jar,.csv,.json,.pdf,.jpg,.png,.jpeg,.doc,.docx,.xlsx,.txt,.der,.cer,.pem,.crt,.pfx,.p12,.jks"
           action=""
-          :limit="fileNumLimit"
           multiple
           :show-file-list="false"
           :before-upload="beforeUploadFile"
@@ -68,7 +66,6 @@
             style="width: 38px; float: left;"
             accept=".jmx,.jar,.csv,.json,.pdf,.jpg,.png,.jpeg,.doc,.docx,.xlsx,.txt,.der,.cer,.pem,.crt,.pfx,.p12,.jks"
             action=""
-            :limit="fileNumLimit"
             :show-file-list="false"
             :before-upload="beforeUpdateUploadFile"
             :http-request="handleUpdateUpload"
@@ -132,7 +129,6 @@ export default {
       loadType: 'jmx',
       existFiles: [],
       selectIds: new Set,
-      fileNumLimit: 10,
       condition: {},
       projectId: getCurrentProjectID()
     };