remove legacy datachannel code

BUG=webrtc:6625

Change-Id: Ic869c28fe9a24147338b5cd2c830a86b008212f9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/244506
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#35634}
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index 0bd3f27..bd90711 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -297,7 +297,6 @@
     bool disable_ipv6_on_wifi;
     int max_ipv6_networks;
     bool disable_link_local_networks;
-    bool enable_rtp_data_channel;
     absl::optional<int> screencast_min_bitrate;
     absl::optional<bool> combined_audio_video_bwe;
     absl::optional<bool> enable_dtls_srtp;