Delete deprecated constructor of SendSideCongestionController.

Move packet_router #include to where it's needed, and delete unused
MockPacketRouter.

Bug: webrtc:6847
Change-Id: I03c86c6fb8b413f5a535a237fa1724cc10960ffa
Reviewed-on: https://webrtc-review.googlesource.com/17320
Commit-Queue: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20564}

call/BUILD.gn

@@ -84,6 +84,7 @@ rtc_source_set("rtp_sender") {
     ":rtp_interfaces",
     "..:webrtc_common",
     "../modules/congestion_controller",
+    "../modules/pacing",
     "../rtc_base:rtc_base_approved",
   ]
 }

call/rtp_transport_controller_send.h

@@ -14,6 +14,7 @@
 #include "call/rtp_transport_controller_send_interface.h"
 #include "common_types.h"  // NOLINT(build/include)
 #include "modules/congestion_controller/include/send_side_congestion_controller.h"
+#include "modules/pacing/packet_router.h"
 #include "rtc_base/constructormagic.h"
 
 namespace webrtc {