Delete unused BluetoothAudioSink code.

device/bluetooth/bluetooth_adapter_unittest.cc

Index: device/bluetooth/bluetooth_adapter_unittest.cc
diff --git a/device/bluetooth/bluetooth_adapter_unittest.cc b/device/bluetooth/bluetooth_adapter_unittest.cc
index 24a77b7f51ab66dec6ec0ffa936877f4c261624d..06829a88dd6d1887fcf14d537b923cb42bd52a56 100644
--- a/device/bluetooth/bluetooth_adapter_unittest.cc
+++ b/device/bluetooth/bluetooth_adapter_unittest.cc
@@ -94,11 +94,6 @@ class TestBluetoothAdapter : public BluetoothAdapter {
       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,