Remove assert which was incorrectly added to TcpPort::OnSentPacket.

TBR=pthatcher@webrtc.org

BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1588083002 .

Cr-Commit-Position: refs/heads/master@{#11252}

webrtc/p2p/base/tcpport.cc

@@ -289,7 +289,6 @@ void TCPPort::OnReadPacket(rtc::AsyncPacketSocket* socket,
 
 void TCPPort::OnSentPacket(rtc::AsyncPacketSocket* socket,
                            const rtc::SentPacket& sent_packet) {
-  ASSERT(socket == socket_);
   PortInterface::SignalSentPacket(sent_packet);
 }