[iOS] Add a PRESUBMIT check for pipes in comments

This CL adds a check to prevent adding additional pipes to disambiguate
symbols and variables in comments. Backticks should be used instead.

Bug: 1311955
Change-Id: Ib0bef6ba7692200c40fe91fbb6781ed173cfc84f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3892349
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1046855}