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

Bug: webrtc:12338
Change-Id: I85bff694dd2ead83c939c4d1945eff82e1296001
No-Presubmit: True
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/227161
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34690}
diff --git a/modules/audio_processing/include/audio_processing_statistics.h b/modules/audio_processing/include/audio_processing_statistics.h
index 87babee..c81d7eb 100644
--- a/modules/audio_processing/include/audio_processing_statistics.h
+++ b/modules/audio_processing/include/audio_processing_statistics.h
@@ -50,9 +50,9 @@
   // The delay metrics consists of the delay median and standard deviation. It
   // also consists of the fraction of delay estimates that can make the echo
   // cancellation perform poorly. The values are aggregated until the first
-  // call to |GetStatistics()| and afterwards aggregated and updated every
+  // call to `GetStatistics()` and afterwards aggregated and updated every
   // second. Note that if there are several clients pulling metrics from
-  // |GetStatistics()| during a session the first call from any of them will
+  // `GetStatistics()` during a session the first call from any of them will
   // change to one second aggregation window for all.
   absl::optional<int32_t> delay_median_ms;
   absl::optional<int32_t> delay_standard_deviation_ms;
@@ -64,7 +64,7 @@
 
   // The instantaneous delay estimate produced in the AEC. The unit is in
   // milliseconds and the value is the instantaneous value at the time of the
-  // call to |GetStatistics()|.
+  // call to `GetStatistics()`.
   absl::optional<int32_t> delay_ms;
 };