!8388 翻译完成：7969 ServiceExtensionAbility开发指导错误示例代码修改

Merge pull request !8388 from wusongqing/TR7969

en/application-dev/ability/stage-serviceextension.md

@@ -42,7 +42,9 @@ OpenHarmony does not support creation of a Service Extension ability for third-p
 2. Customize a class that inherits from **ServiceExtensionAbility** in the .ts file in the directory where the Service Extension ability is defined and override the lifecycle callbacks of the base class. The code sample is as follows:
 
     ```js
+    import ServiceExtensionAbility from '@ohos.application.ServiceExtensionAbility'
     import rpc from '@ohos.rpc'
+
     class StubTest extends rpc.RemoteObject {
         constructor(des) {
             super(des);
@@ -51,7 +53,8 @@ OpenHarmony does not support creation of a Service Extension ability for third-p
         }
     }
 
-    class ServiceExt extends ServiceExtensionAbility {
+    class ServiceExtAbility extends ServiceExtensionAbility {
+        onCreate(want) {
             console.log('onCreate, want:' + want.abilityName);
         }
         onRequest(want, startId) {