Remove linux-lacros-tester-rel builder

Bug: 347103477
Change-Id: Iaca60b0c3790e7b6a96db63518faa72e5aa90f64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5805243


Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Auto-Submit: Sven Zheng <svenzheng@chromium.org>
Reviewed-by: Wanda Mora <morawand@google.com>
Commit-Queue: Wanda Mora <morawand@google.com>
Cr-Commit-Position: refs/heads/main@{#1345053}