Use backticks not vertical bars to denote variables in comments

Bug: webrtc:12338
Change-Id: I89c8b3a328d04203177522cbdfd9e606fd4bce4c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/228246
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34696}
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 047776b..6761ed4 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -570,8 +570,8 @@
   // The int16 interfaces require:
   //   - only `NativeRate`s be used
   //   - that the input, output and reverse rates must match
-  //   - that |processing_config.output_stream()| matches
-  //     |processing_config.input_stream()|.
+  //   - that `processing_config.output_stream()` matches
+  //     `processing_config.input_stream()`.
   //
   // The float interfaces accept arbitrary rates and support differing input and
   // output layouts, but the output must have either one channel or the same