This removes (now unused) the legacy ICE controller code paths from P2PTransportChannel. Bug: webrtc:14367 Change-Id: I53dc7ee46ec844d20331e2622fa99dbe8b740ad6 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/294291 Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Sameer Vijaykar <samvi@google.com> Cr-Commit-Position: refs/heads/main@{#39398}