Delete unused BluetoothAudioSink code.

device/bluetooth/bluetooth_adapter_mac.mm

Index: device/bluetooth/bluetooth_adapter_mac.mm
diff --git a/device/bluetooth/bluetooth_adapter_mac.mm b/device/bluetooth/bluetooth_adapter_mac.mm
index 3bc426e6a45440211692b68e368565da68ece1ad..61d169e2c21937557362c21eb9b3d2f77e15d2f5 100644
--- a/device/bluetooth/bluetooth_adapter_mac.mm
+++ b/device/bluetooth/bluetooth_adapter_mac.mm
@@ -195,14 +195,6 @@ void BluetoothAdapterMac::CreateL2capService(
       this, uuid, options, base::Bind(callback, socket), error_callback);
 }
 
-void BluetoothAdapterMac::RegisterAudioSink(
-    const BluetoothAudioSink::Options& options,
-    const AcquiredCallback& callback,
-    const BluetoothAudioSink::ErrorCallback& error_callback) {
-  NOTIMPLEMENTED();
-  error_callback.Run(BluetoothAudioSink::ERROR_UNSUPPORTED_PLATFORM);
-}
-
 void BluetoothAdapterMac::RegisterAdvertisement(
     std::unique_ptr<BluetoothAdvertisement::Data> advertisement_data,
     const CreateAdvertisementCallback& callback,