Remove pointless move() to fix build on clang/win.

Fixes:
..\..\third_party\libjingle\source\talk\app\webrtc\remoteaudiosource.cc(100,15)
: error: moving a temporary object prevents copy elision
[-Werror,-Wpessimizing-move]
        ssrc, std::move(rtc::scoped_ptr<AudioSinkInterface>(new Sink(this))));
              ^
..\..\third_party\libjingle\source\talk\app\webrtc\remoteaudiosource.cc(100,15)
:  note: remove std::move call here
        ssrc, std::move(rtc::scoped_ptr<AudioSinkInterface>(new Sink(this))));
              ^~~~~~~~~~

R=thakis@chromium.org
TBR=thakis@chromium.org

Review URL: https://codereview.webrtc.org/1517253004 .

Cr-Commit-Position: refs/heads/master@{#10999}