Drop the rtp_rtcp module's dependency on call.

Also deletes a couple of includes of call.h, which seem
unnecessary.

BUG=None

Review-Url: https://codereview.webrtc.org/2907403003
Cr-Commit-Position: refs/heads/master@{#18340}

webrtc/modules/rtp_rtcp/source/rtcp_sender.cc

@@ -18,7 +18,6 @@
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/trace_event.h"
-#include "webrtc/call/call.h"
 #include "webrtc/common_types.h"
 #include "webrtc/logging/rtc_event_log/rtc_event_log.h"
 #include "webrtc/modules/rtp_rtcp/source/rtcp_packet/app.h"