update backgroundImageSize docs

Signed-off-by: Nchenyuhuai <chenyuhuai1@huawei.com>

zh-cn/application-dev/reference/arkui-ts/ts-universal-attributes-backgroundBlurStyle.md

@@ -32,7 +32,6 @@
 // xxx.ets
 @Entry
 @Component
-
 struct Index {
   build() {
     Column() {
@@ -42,12 +41,13 @@ struct Index {
       .width(350)
       .height(300)
       .backgroundBlurStyle(BlurStyle.Thin)
-      .position({x: "15%", y: "30%"})
+      .position({ x: "15%", y: "30%" })
     }
     .height('100%')
     .width('100%')
     .backgroundImage($r('app.media.bg'))
     .backgroundImageSize(ImageSize.Cover)
   }
+}
 ```
 ![zh-cn_image_background_blur_style](figures/zh-cn_image_background_blur_style.png)
\ No newline at end of file