format change

Signed-off-by: Nzhangxin_T <zhangxin312@huawei.com>

zh-cn/application-dev/background-task-management/background-task-dev-guide.md

@@ -33,32 +33,35 @@ import backgroundTaskManager from '@ohos.backgroundTaskManager';
 
 
 1. 申请延迟挂起
-   ```js
-   import backgroundTaskManager from '@ohos.backgroundTaskManager';
-   let myReason = 'test requestSuspendDelay';
-   let delayInfo = backgroundTaskManager.requestSuspendDelay(myReason, () => {
-       console.info("Request suspension delay will time out.");
-   });
-   var id = delayInfo.requestId;console.info("requestId is: " + id);
-   ```
+
+```js
+import backgroundTaskManager from '@ohos.backgroundTaskManager';
+
+let myReason = 'test requestSuspendDelay';
+let delayInfo = backgroundTaskManager.requestSuspendDelay(myReason, () => {
+    console.info("Request suspension delay will time out.");
+});
+
+var id = delayInfo.requestId;console.info("requestId is: " + id);
+```
 
 
 2. 获取进入挂起前的剩余时间
 
-    ```js
-    backgroundTaskManager.getRemainingDelayTime(id).then( res => {
-        console.log('promise => Operation succeeded. Data: ' + JSON.stringify(res));
-    }).catch( err => {
-        console.log('promise => Operation failed. Cause: ' + err.data);
-    });
-    ```
+```js
+backgroundTaskManager.getRemainingDelayTime(id).then( res => {
+    console.log('promise => Operation succeeded. Data: ' + JSON.stringify(res));
+}).catch( err => {
+    console.log('promise => Operation failed. Cause: ' + err.data);
+});
+```
 
 
 3. 取消延迟挂起
 
-    ```js
-    backgroundTaskManager.cancelSuspendDelay(id);
-    ```
+```js
+backgroundTaskManager.cancelSuspendDelay(id);
+```
 
 
 ## 开发实例