fixed 0c5fbabc from https://gitee.com/HelloCrease/docs/pulls/3399

update zh-cn/application-dev/ui/ui-js-components-button.md.
Signed-off-by: NLiAn <lian15@huawei.com>

zh-cn/application-dev/ui/ui-js-components-button.md

@@ -157,7 +157,7 @@ export default {
  setProgress(e) {
     if(this.isPaused){
       prompt.showToast({
-        message: "Started Ddownloading"
+        message: "Started Downloading"
       })
       this.star();
       this.isPaused = false;