removed unused import

Author: gonzalonarbaiz

OneSignalSDK/onesignal/src/main/java/com/onesignal/OneSignal.java

@@ -46,7 +46,6 @@
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.annotation.WorkerThread;
 import androidx.core.app.NotificationCompat;