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