Remove the unused and untested functions from VoERTP_RTCP.

BUG=webrtc:4690

Review-Url: https://codereview.webrtc.org/2667423004
Cr-Original-Commit-Position: refs/heads/master@{#16606}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 81d93f37a5df59eadff2d5aed3d187b78c39fcd7
6 files changed