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

Bug: webrtc:12338
Change-Id: Ib97b2c3d64dbd895f261ffa76a2e885bd934a87f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226940
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34554}
diff --git a/api/audio_codecs/audio_format.h b/api/audio_codecs/audio_format.h
index 9f61729..0cf6779 100644
--- a/api/audio_codecs/audio_format.h
+++ b/api/audio_codecs/audio_format.h
@@ -39,7 +39,7 @@
                  Parameters&& param);
   ~SdpAudioFormat();
 
-  // Returns true if this format is compatible with |o|. In SDP terminology:
+  // Returns true if this format is compatible with `o`. In SDP terminology:
   // would it represent the same codec between an offer and an answer? As
   // opposed to operator==, this method disregards codec parameters.
   bool Matches(const SdpAudioFormat& o) const;