[Lacros] Modify tast_expr to run tast tests

Run the command in chroot:
tast list -checktestdeps localhost:2222
'("group:mainline" && "dep:lacros" && !informational)'
it returns:
lacros.AppLauncherLaunch
lacros.AudioPlay
lacros.Basic
lacros.ShelfLaunch

That's the tast tests we want to run.

Bug: 1273637
Change-Id: I4c1ec3f088745ee284fd150247d63d804a6cc20e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3373213


Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Jieting Yang <yjt@google.com>
Cr-Commit-Position: refs/heads/main@{#958196}