Remove unused function implementations from FakeWebRtcVoiceEngine.

BUG=webrtc:4690

Review-Url: https://codereview.webrtc.org/2440353003
Cr-Original-Commit-Position: refs/heads/master@{#14752}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 88b70747451a41a1d0f8dc607c959ce8548d83cb
1 file changed