update js-apis-fileio.md

Signed-off-by: Nraoxian <raoxian@huawei.com>

zh-cn/application-dev/reference/apis/js-apis-fileio.md

@@ -595,7 +595,7 @@ openSync(path:string, flags?:number, mode?:number): number
 
 **示例：**
   ```js
-  let fd = fileio.openSync(path);
+  let fd = fileio.openSync(path, 0o102, 0o640);
   ```