Bass: Use checking if broadcast is active instead of synced to BISes

Swap method isAnyReceiverReceivingBroadcast to isAnyReceiverActive where
is check of syncing to PA or BISes instead of check only syncing to BISes.

Method is used only in LeAudioService#isGroupReceivingBroadcast so checking active has more sens as unsyncing from BISes could be unintentional i.e. when music is paused.

Bug: 378615357
Bug: EXEMPT; simple change covered with unit test
Test: atest BassClientServiceTest
Change-Id: Idf2506d072494287c7b113beed2c27222bbbba67