remove deprecated fields in rtc::NetworkRoute

this patch is a followup to https://webrtc-review.googlesource.com/c/src/+/170628
and removed the now deprecated fields {local/remote}_network_id that
is now no longer used by downstream.

BUG: webrtc:11434
Change-Id: Ia322609c0b4f07b05b8592cbca7f001a115da109
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/171515
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30874}
diff --git a/p2p/base/p2p_transport_channel.cc b/p2p/base/p2p_transport_channel.cc
index d935a45..2a4ad59 100644
--- a/p2p/base/p2p_transport_channel.cc
+++ b/p2p/base/p2p_transport_channel.cc
@@ -1733,12 +1733,6 @@
         /* uses_turn= */ selected_connection_->remote_candidate().type() ==
             RELAY_PORT_TYPE);
 
-    // Downstream projects depend on the old representation,
-    // populate that until they have been migrated.
-    // TODO(jonaso): remove.
-    network_route_->local_network_id = network_route_->local.network_id();
-    network_route_->remote_network_id = network_route_->remote.network_id();
-
     network_route_->last_sent_packet_id = last_sent_packet_id_;
     network_route_->packet_overhead =
         selected_connection_->local_candidate().address().ipaddr().overhead() +
diff --git a/rtc_base/network_route.h b/rtc_base/network_route.h
index c97c6ea..f7991c8 100644
--- a/rtc_base/network_route.h
+++ b/rtc_base/network_route.h
@@ -71,12 +71,6 @@
   // This is the maximum of any part of the route.
   int packet_overhead = 0;
 
-  // Downstream projects depend on the old representation,
-  // populate that until they have been migrated.
-  // TODO(jonaso): remove.
-  uint16_t local_network_id = 0;
-  uint16_t remote_network_id = 0;
-
   RTC_NO_INLINE inline std::string DebugString() const {
     rtc::StringBuilder oss;
     oss << "[ connected: " << connected << " local: [ " << local.adapter_id()