fixed 4d0b0067 from https://gitee.com/onexiaomin/docs/pulls/13359

adapt to some changes
Signed-off-by: Nonexiaomin <wangminmin4@huawei.com>

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

@@ -10,7 +10,7 @@
 ## 导入模块
 
 ```js
-import fileExtensionInfo from '@ohos.fileExtensionInfo';
+import fileExtensionInfo from '@ohos.file.fileExtensionInfo';
 ```
 
 ## fileExtensionInfo.DeviceType