Delete unused BluetoothAudioSink code.

device/bluetooth/bluetooth_adapter_mac.h

Index: device/bluetooth/bluetooth_adapter_mac.h
diff --git a/device/bluetooth/bluetooth_adapter_mac.h b/device/bluetooth/bluetooth_adapter_mac.h
index 994610b4a5f2cba5a7ece47b517b1c32764bcb38..6ef24f430cddb771ebd09743fbd78b822b416652 100644
--- a/device/bluetooth/bluetooth_adapter_mac.h
+++ b/device/bluetooth/bluetooth_adapter_mac.h
@@ -18,7 +18,6 @@
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "device/bluetooth/bluetooth_adapter.h"
-#include "device/bluetooth/bluetooth_audio_sink.h"
 #include "device/bluetooth/bluetooth_discovery_manager_mac.h"
 #include "device/bluetooth/bluetooth_export.h"
 #include "device/bluetooth/bluetooth_low_energy_device_mac.h"
@@ -82,10 +81,6 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterMac
       const ServiceOptions& options,
       const CreateServiceCallback& callback,
       const CreateServiceErrorCallback& error_callback) override;
-  void RegisterAudioSink(
-      const BluetoothAudioSink::Options& options,
-      const AcquiredCallback& callback,
-      const BluetoothAudioSink::ErrorCallback& error_callback) override;
   void RegisterAdvertisement(
       std::unique_ptr<BluetoothAdvertisement::Data> advertisement_data,
       const CreateAdvertisementCallback& callback,