update zh-cn/application-dev/reference/apis/js-apis-pasteboard.md.

Signed-off-by: Nsunyue <sunyue77@h-partners.com>

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

@@ -914,7 +914,7 @@ on(type:  'update', callback: () =>void ): void
 
   ```js
   var systemPasteboard = pasteboard.getSystemPasteboard();
-  var listener = ()=>{
+  var listener = () = > {
       console.info('The system pasteboard has changed');
   };
   systemPasteboard.on('update', listener);
@@ -938,7 +938,7 @@ off(type:  'update', callback?: () =>void ): void
 **示例**
 
   ```js
-  var listener = ()=>{
+  let listener = () = > {
       console.info('The system pasteboard has changed');
   };
   systemPasteboard.off('update', listener);