Remove unused member variable - RTCPSender::using_nack_

Bug: None
Change-Id: I346c6a195d2d21387f89e41cfc070f33466ef195
Reviewed-on: https://webrtc-review.googlesource.com/c/109462
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Elad Alon <eladalon@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25512}
diff --git a/modules/rtp_rtcp/source/rtcp_sender.cc b/modules/rtp_rtcp/source/rtcp_sender.cc
index 67fdf34..ac50b32 100644
--- a/modules/rtp_rtcp/source/rtcp_sender.cc
+++ b/modules/rtp_rtcp/source/rtcp_sender.cc
@@ -126,7 +126,6 @@
       event_log_(event_log),
       transport_(outgoing_transport),
       interval_config_(interval_config),
-      using_nack_(false),
       sending_(false),
       next_time_to_send_rtcp_(0),
       timestamp_offset_(0),
diff --git a/modules/rtp_rtcp/source/rtcp_sender.h b/modules/rtp_rtcp/source/rtcp_sender.h
index 8570591..2720e0a 100644
--- a/modules/rtp_rtcp/source/rtcp_sender.h
+++ b/modules/rtp_rtcp/source/rtcp_sender.h
@@ -193,7 +193,6 @@
   const RtcpIntervalConfig interval_config_;
 
   rtc::CriticalSection critical_section_rtcp_sender_;
-  bool using_nack_ RTC_GUARDED_BY(critical_section_rtcp_sender_);
   bool sending_ RTC_GUARDED_BY(critical_section_rtcp_sender_);
 
   int64_t next_time_to_send_rtcp_ RTC_GUARDED_BY(critical_section_rtcp_sender_);