style(android): remove unused import

Author: erisu

src/android/Notification.java

@@ -22,7 +22,6 @@ Licensed to the Apache Software Foundation (ASF) under one
 import android.app.AlertDialog;
 import android.app.AlertDialog.Builder;
 import android.app.ProgressDialog;
-import android.content.DialogInterface;
 import android.content.res.Resources;
 import android.media.Ringtone;
 import android.media.RingtoneManager;