[iOS] Change pipes to backticks in /ios/chrome/browser/policy

Please review the CL to ensure that nothing is broken and the script
didn't miss some pipes.

This should allow us to have a better formatting in Xcode.

This CL was uploaded by git cl split.

R=zmin@chromium.org

Bug: 1311955
Change-Id: Ib7031f8fc541193effdd41b4b0910459568bfb56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3857543


Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1040851}