Also removing some related code that appears to be unused. This is a part of simplifying the RtpRtcpInterface implementation. Bug: webrtc:11581 Change-Id: I580bfdc1b821d571cb7437d7713a49ee4de2d19a Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176568 Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Tommi <tommi@webrtc.org> Cr-Commit-Position: refs/heads/master@{#31464}