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/acm2/acm_receive_test.h b/modules/audio_coding/acm2/acm_receive_test.h
index 043092c..6349c63 100644
--- a/modules/audio_coding/acm2/acm_receive_test.h
+++ b/modules/audio_coding/acm2/acm_receive_test.h
@@ -71,8 +71,8 @@
   RTC_DISALLOW_COPY_AND_ASSIGN(AcmReceiveTestOldApi);
 };
 
-// This test toggles the output frequency every |toggle_period_ms|. The test
-// starts with |output_freq_hz_1|. Except for the toggling, it does the same
+// This test toggles the output frequency every `toggle_period_ms`. The test
+// starts with `output_freq_hz_1`. Except for the toggling, it does the same
 // thing as AcmReceiveTestOldApi.
 class AcmReceiveTestToggleOutputFreqOldApi : public AcmReceiveTestOldApi {
  public: