Update QS menu to say "Shut down" instead of power off

Bug: b/295040745
Change-Id: Idda0d83334454e5329a24d2114938d481e75411e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4787133


Commit-Queue: Jiaming Cheng <jiamingc@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1184836}