Update documentation

Test: NotificationManagerTest
Fixes: 264140399
Change-Id: Ied8cb94295538ded6dba998a3ceacc4ba9c576d9
diff --git a/core/java/android/service/notification/NotificationListenerService.java b/core/java/android/service/notification/NotificationListenerService.java
index e55e2e5..d39a6ea 100644
--- a/core/java/android/service/notification/NotificationListenerService.java
+++ b/core/java/android/service/notification/NotificationListenerService.java
@@ -77,6 +77,7 @@
  * <pre>
  * &lt;service android:name=".NotificationListener"
  *          android:label="&#64;string/service_name"
+ *          android:exported="false"
  *          android:permission="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE">
  *     &lt;intent-filter>
  *         &lt;action android:name="android.service.notification.NotificationListenerService" />