leaudio_test: Fix Mock::VerifyAndClearExpectations

Both mock_le_audio_sink_hal_client_ and mock_le_audio_source_hal_client_
are already a pointers and shall be pass to  Mock::VerifyAndClearExpectations
as is.

The above change also revealed the issue in the test:
SetAndClearSinkMonitorModeWhileUnicastIsInactive

Bug: 331775328
Flag: TEST_ONLY
Test: atest bluetooth_le_audio_client_test
Change-Id: I42551a12837907ac3afa3ef71a8d25a75d131cfb