update docs against 6610

Signed-off-by: Nwusongqing <wusongqing@huawei.com>

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

@@ -300,7 +300,7 @@ export default class MainAbility extends Ability {
 
 Obtain the `want` parameter that contains the page information from the custom component and process the route based on the URI.
 ```ts
-import router from '@system.router'
+import router from '@ohos.router'
 
 @Entry
 @Component