Opp: Fix that group summary notification does not disappear

Bug: 393984953
Bug: 395546332
Flag: com.android.bluetooth.flags.opp_remove_empty_group_notification
Test: m -j;
Test: Manual, send/receive files and open the files,
      the notification group summary should disappear
Change-Id: I4585bf4dbfc93ba23e20526ea0ae6339d90e3f88