Hide incomplete feature.

Test: make
Change-Id: I505a8ee2f2fbdb574f607005579832951f28022a
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 97fbfa5..3ca2208 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -3076,10 +3076,11 @@
     <permission android:name="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE"
         android:protectionLevel="signature" />
 
-    <!-- Must be required by an {@link
+    <!-- @SystemApi Must be required by an {@link
          android.service.notification.NotificationAssistantService} to ensure that only the system
          can bind to it.
          <p>Protection level: signature
+         @hide
     -->
     <permission android:name="android.permission.BIND_NOTIFICATION_ASSISTANT_SERVICE"
         android:protectionLevel="signature" />