Fixed warning

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -108,7 +108,6 @@ import javax.mail.search.ReceivedDateTerm;
 import javax.net.ssl.SSLException;
 
 import androidx.annotation.Nullable;
-import androidx.core.app.NotificationCompat;
 import androidx.core.content.ContextCompat;
 import androidx.lifecycle.LifecycleService;
 import androidx.lifecycle.Observer;