Grant abandon to chromeos-prod-bot

PUpr jobs sometimes try and abandon previous CLs.

Bug: b/406133835

Change-Id: I62838094ef8f72301b15a3b3c064c71c3d428bed
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/+/6394597
Reviewed-by: Mike Frysinger <vapier@chromium.org>