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

Bug: webrtc:12338
Change-Id: I72fcb505a92f03b2ace7160ee33d555a977eddfd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226955
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34587}

rtc_base/virtual_socket_server.h

diff --git a/rtc_base/virtual_socket_server.h b/rtc_base/virtual_socket_server.h
index 6c58a4bd..af86991 100644
--- a/rtc_base/virtual_socket_server.h
+++ b/rtc_base/virtual_socket_server.h
@@ -104,10 +104,10 @@
 
   size_t largest_seen_udp_payload() { return largest_seen_udp_payload_; }
 
-  // If |blocked| is true, subsequent attempts to send will result in -1 being
+  // If `blocked` is true, subsequent attempts to send will result in -1 being
   // returned, with the socket error set to EWOULDBLOCK.
   //
-  // If this method is later called with |blocked| set to false, any sockets
+  // If this method is later called with `blocked` set to false, any sockets
   // that previously failed to send with EWOULDBLOCK will emit SignalWriteEvent.
   //
   // This can be used to simulate the send buffer on a network interface being