Update test for Truth8 deprecation.

Truth8 is now included in Truth and importing both no longer
works in version 1.4.0.

Bug: 369506710
Test: presubmit, m BumbleBluetoothTestsApp
Flag: EXEMPT test-only change
Change-Id: Idaf8e52e51efa0e260febe1562c37faedb4781f6