Add anqing@ into Kiosk OWNERS

anqing@ need to get sign-off permission to review Kiosk code changes.

Change-Id: I69c4101f987334a7bd69ce48b259e1ec1e110cea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2116431Reviewed-by: Anatoliy Potapchuk <apotapchuk@chromium.org>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Anqing Zhao <anqing@google.com>
Cr-Commit-Position: refs/heads/master@{#752814}

chrome/browser/chromeos/app_mode/OWNERS

+anqing@chromium.org
 apotapchuk@chromium.org
 poromov@chromium.org