fixed b0ae5c77 from https://gitee.com/HelloCrease/docs/pulls/16148

update zh-cn/application-dev/reference/arkui-ts/ts-container-flex.md.
Signed-off-by: NLiAn <lian15@huawei.com>
Signed-off-by: NLiAn <lian15@huawei.com>

zh-cn/application-dev/reference/arkui-ts/ts-container-flex.md

@@ -143,7 +143,7 @@ struct FlexExample2 {
 }
 ```
 
-![zh-cn_image_0000001174264366](figures/zh-cn_image_0000001174264366.PNG)
+![zh-cn_image_0000001174264366](figures/zh-cn_image_0000001174264366.png)
 
 ```ts
 // xxx.ets