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/rms_level.h b/modules/audio_processing/rms_level.h
index e1a6d56..4955d1b 100644
--- a/modules/audio_processing/rms_level.h
+++ b/modules/audio_processing/rms_level.h
@@ -47,7 +47,7 @@
   void Analyze(rtc::ArrayView<const int16_t> data);
   void Analyze(rtc::ArrayView<const float> data);
 
-  // If all samples with the given |length| have a magnitude of zero, this is
+  // If all samples with the given `length` have a magnitude of zero, this is
   // a shortcut to avoid some computation.
   void AnalyzeMuted(size_t length);
 
@@ -62,7 +62,7 @@
   Levels AverageAndPeak();
 
  private:
-  // Compares |block_size| with |block_size_|. If they are different, calls
+  // Compares `block_size` with `block_size_`. If they are different, calls
   // Reset() and stores the new size.
   void CheckBlockSize(size_t block_size);