Revoke access to .Xauthority from CrOS GPU sandbox.

This CL removes the permission that's set to allow read-only access to
/home/chronos/.Xauthority in AddArmGpuPermissions() which should only be
reached on ChromeOS. This seems like a relic from the past since we
don't use X on ChromeOS nowadays.

Bug: 1339079
Test: None
Change-Id: Ifc8d445e3aea82ec7ba1176547397b9a6a3d662f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3813542
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Auto-Submit: Andres Calderon Jaramillo <andrescj@chromium.org>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1032718}