[Lacros] Remove " - Google Chrome" suffix from browser window title

Per the latest product guideline [1], in ChromeOS desk overview mode,
the title of Lacros window should not contain the " - Google Chrome"
suffix. For context, Ash does not have this suffix. This CL is to remove
the suffix for Lacros.

This CL does not break any Tast test as far as I can tell. Though I do
plan to immediately update related functions such as [2] in the ChromeOS
Tast repo to more accurately document the latest product decision and
the subtleties it entails.

[1] https://crbug.com/1280197#c12
[2] https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/platform/tast-tests/src/chromiumos/tast/local/chrome/ash/wm.go;l=920?q=ash.browsertitlematch

Bug: 1280197
Test: Browser tests
Change-Id: I7e6e7739e8724af9c82bd1003e184e30c56bd23f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4364105
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Di Wu <diwux@google.com>
Cr-Commit-Position: refs/heads/main@{#1127020}