Remove the ID from AcmReceiver

This is an artifact from the past, and is no longer used.

R=ivoc@webrtc.org

Review URL: https://codereview.webrtc.org/1764623002

Cr-Commit-Position: refs/heads/master@{#11866}
diff --git a/webrtc/modules/audio_coding/acm2/acm_receiver.cc b/webrtc/modules/audio_coding/acm2/acm_receiver.cc
index 53ec884..39d8a0d 100644
--- a/webrtc/modules/audio_coding/acm2/acm_receiver.cc
+++ b/webrtc/modules/audio_coding/acm2/acm_receiver.cc
@@ -118,8 +118,7 @@
 }  // namespace
 
 AcmReceiver::AcmReceiver(const AudioCodingModule::Config& config)
-    : id_(config.id),
-      last_audio_decoder_(nullptr),
+    : last_audio_decoder_(nullptr),
       previous_audio_activity_(AudioFrame::kVadPassive),
       audio_buffer_(new int16_t[AudioFrame::kMaxDataSizeSamples]),
       last_audio_buffer_(new int16_t[AudioFrame::kMaxDataSizeSamples]),
@@ -419,11 +418,6 @@
   return 0;
 }
 
-void AcmReceiver::set_id(int id) {
-  rtc::CritScope lock(&crit_sect_);
-  id_ = id;
-}
-
 bool AcmReceiver::GetPlayoutTimestamp(uint32_t* timestamp) {
   return neteq_->GetPlayoutTimestamp(timestamp);
 }