Opp: Fix 'Sent/Received files' notifications being swiped out together

Bug: 323093937
Bug: 323096132
Test: atest BluetoothOppReceiverTest BluetoothOppTransferHistoryTest
Test: Manual, after receiving and sending a file via bluetooth,
      swipe out the 'Received files' notification. Then 'Sent files'
      notification should not disappear (vice versa).
Change-Id: I73896b081efc7c20c8d1d677f58f25fb7f34550c