OPP: Do not use group summary for 'Sent/Received files' notification

Bug: 395546332
Bug: 393984953
Test: m -j;
Test: Receive/Send file via OPP and check the received file from
      notification. There should be no empty notification
Change-Id: If4f99c5573da5c90b492243d1e5b834f949cbf48