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

Bug: webrtc:12338
Change-Id: I753a476d1574d8dd50f1b6d4bfc2beb7f6f1f913
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226947
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34562}

examples/objc/AppRTCMobile/ios/ARDMainView.m

@@ -64,7 +64,7 @@ static CGFloat const kCallControlMargin = 8;
 
 - (BOOL)textFieldShouldReturn:(UITextField *)textField {
   // There is no other control that can take focus, so manually resign focus
-  // when return (Join) is pressed to trigger |textFieldDidEndEditing|.
+  // when return (Join) is pressed to trigger `textFieldDidEndEditing`.
   [textField resignFirstResponder];
   return YES;
 }