Use backticks not vertical bars to denote variables in comments for /modules/audio_coding

Bug: webrtc:12338
Change-Id: I02613d9fca45d00e2477f334b7a0416e7912e26b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/227037
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34621}
diff --git a/modules/audio_coding/neteq/decoder_database_unittest.cc b/modules/audio_coding/neteq/decoder_database_unittest.cc
index 33bee8d..f28a0fd 100644
--- a/modules/audio_coding/neteq/decoder_database_unittest.cc
+++ b/modules/audio_coding/neteq/decoder_database_unittest.cc
@@ -148,7 +148,7 @@
   }
   PacketList packet_list;
   for (int i = 0; i < kNumPayloads + 1; ++i) {
-    // Create packet with payload type |i|. The last packet will have a payload
+    // Create packet with payload type `i`. The last packet will have a payload
     // type that is not registered in the decoder database.
     Packet packet;
     packet.payload_type = i;