Revert "Use lkgm file for Lacros public builders"

This reverts commit 680ffd20.

Reason for revert: Broke dawn roll

BUG=331775413
Original change's description:
> Use lkgm file for Lacros public builders
>
> Use lkgm version from //chromeos/CHROMEOS_LKGM instead of
> the buildbot config.
>
> Change-Id: Iece7ed466cad621eee91e10e6293c8c409f3f724
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5384923


> Commit-Queue: Sven Zheng <svenzheng@chromium.org>
> Reviewed-by: Kuan Huang <kuanhuang@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1278672}

Change-Id: Ibf7b361022b3af9bc94fbb41f19902d0b99033fe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5407354
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Sven Zheng <svenzheng@chromium.org>
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1280206}