message: Make MockRtpTransceiver not inherit from RefCountedObject
  Cr-Commit-Position: refs/heads/main@{#36279}
diff: namespace webrtc {
  -class MockRtpTransceiver final
  - : public rtc::RefCountedObject<RtpTransceiverInterface> {
  +class MockRtpTransceiver : public RtpTransceiverInterface {
  public:
  + MockRtpTransceiver() = default;
  +
  static rtc::scoped_refptr<MockRtpTransceiver> Create() {
  - return rtc::scoped_refptr<MockRtpTransceiver>(new MockRtpTransceiver());
  + return rtc::make_ref_counted<MockRtpTransceiver>();
  }
  MOCK_METHOD(cricket::MediaType, media_type, (), (const, override));
  @@ -79,9 +80,6 @@ class MockRtpTransceiver final
  (rtc::ArrayView<const RtpHeaderExtensionCapability>
  header_extensions_to_offer),
  (override));
  -
  - private:
  - MockRtpTransceiver() = default;
  };
  } // namespace webrtc
  