Remove ignored return code from modules.

ModuleProcessImpl doesn't act on return codes and having them around is
confusing (it's unclear what an error return code here would do even).

BUG=
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1703833002 .

Cr-Commit-Position: refs/heads/master@{#11747}
diff --git a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
index 72a5ff5..bf60878 100644
--- a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
+++ b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
@@ -162,16 +162,15 @@
       kBitrateControllerUpdateIntervalMs - time_since_update_ms, 0);
 }
 
-int32_t BitrateControllerImpl::Process() {
+void BitrateControllerImpl::Process() {
   if (TimeUntilNextProcess() > 0)
-    return 0;
+    return;
   {
     rtc::CritScope cs(&critsect_);
     bandwidth_estimation_.UpdateEstimate(clock_->TimeInMilliseconds());
   }
   MaybeTriggerOnNetworkChanged();
   last_bitrate_update_ms_ = clock_->TimeInMilliseconds();
-  return 0;
 }
 
 void BitrateControllerImpl::OnReceivedRtcpReceiverReport(