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/rtc_event_log_output.h b/api/rtc_event_log_output.h
index 92fb9e8..cd16b27 100644
--- a/api/rtc_event_log_output.h
+++ b/api/rtc_event_log_output.h
@@ -29,7 +29,7 @@
   // Write encoded events to an output. Returns true if the output was
   // successfully written in its entirety. Otherwise, no guarantee is given
   // about how much data was written, if any. The output sink becomes inactive
-  // after the first time |false| is returned. Write() may not be called on
+  // after the first time `false` is returned. Write() may not be called on
   // an inactive output sink.
   virtual bool Write(const std::string& output) = 0;