!8758 修复Stage模型ability生命周期中loadcontent示例错误（ data为undefined）

Merge pull request !8758 from 张亚菲/zyf

zh-cn/application-dev/ability/stage-ability.md

@@ -87,7 +87,7 @@ Ability功能如下（Ability类，具体的API详见[接口文档](../reference
     onWindowStageCreate(windowStage) {
         console.log("MainAbility onWindowStageCreate")
 
-        windowStage.loadContent("pages/index").then((data) => {
+        windowStage.loadContent("pages/index").then(() => {
             console.log("MainAbility load content succeed")
         }).catch((error) => {
             console.error("MainAbility load content failed with error: " + JSON.stringify(error))