AudioDeviceBroker: Fix the wrong system property name

The correct system property name is `bluetooth.sco.managed_by_audio`,
not `audio.sco.managed.by.audio` .

See system/libsysprop/srcs/android/sysprop/BluetoothProperties.sysprop

Flag: DOCS_ONLY
Bug: 416640654
Test: m
Change-Id: I0ef6b798e4c66d134a317b8248eb385971ebe111