cas: fix package comment
cas: fix package comment

Bug: 1110569
Change-Id: Icc7cd7b13ce9721148114a5ed1cf1e4c5062417c
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2332137
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
Reviewed-by: Junji Watanabe <aaef61ef98ffea505db831f310be2a0eb8492537@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go