Fix binder leakage when wakelock is released

We were not unsubscribing the callbacks when the wakelocks are released,
but were doing that only when the binder died. This lead to many leaky
binders for the released wakelocks

Bug: 431687714
Flag: com.android.server.power.feature.flags.disable_frozen_process_wakelocks
Test: atest PowerManagerServiceTest
Change-Id: Ifaba8c97ca072735f391ff534e2a134e75d6fba2