Replace "RTRR" with "RRTR"

which is the correct term used in
  https://www.rfc-editor.org/rfc/rfc3611#section-4.4

BUG=None

Change-Id: Iab5a1de6b69a8495aa9a6f79531053f4f2421c27
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/306480
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40143}
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc
index 950bcb9..d183c5b 100644
--- a/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl2_unittest.cc
@@ -442,10 +442,10 @@
 }
 
 TEST_F(RtpRtcpImpl2Test, RttForReceiverOnly) {
-  // Receiver module should send a Receiver time reference report (RTRR).
+  // Receiver module should send a Receiver reference time report block (RRTR).
   EXPECT_EQ(0, receiver_.impl_->SendRTCP(kRtcpReport));
 
-  // Sender module should send a response to the last received RTRR (DLRR).
+  // Sender module should send a response to the last received RRTR (DLRR).
   AdvanceTime(TimeDelta::Millis(1000));
   // Send Frame before sending a SR.
   EXPECT_TRUE(SendFrame(&sender_, sender_video_.get(), kBaseLayerTid));
diff --git a/modules/rtp_rtcp/source/rtp_rtcp_impl_unittest.cc b/modules/rtp_rtcp/source/rtp_rtcp_impl_unittest.cc
index 2c05827..4875ee9 100644
--- a/modules/rtp_rtcp/source/rtp_rtcp_impl_unittest.cc
+++ b/modules/rtp_rtcp/source/rtp_rtcp_impl_unittest.cc
@@ -309,10 +309,10 @@
 }
 
 TEST_F(RtpRtcpImplTest, RttForReceiverOnly) {
-  // Receiver module should send a Receiver time reference report (RTRR).
+  // Receiver module should send a Receiver reference time report block (RRTR).
   EXPECT_EQ(0, receiver_.impl_->SendRTCP(kRtcpReport));
 
-  // Sender module should send a response to the last received RTRR (DLRR).
+  // Sender module should send a response to the last received RRTR (DLRR).
   clock_.AdvanceTimeMilliseconds(1000);
   // Send Frame before sending a SR.
   SendFrame(&sender_, sender_video_.get(), kBaseLayerTid);