copybot.py: Include cherry-picked hash in commit msg

'Sean Paul' bot wants '(cherry picked from XXX)' in commit body.

BUG=b:232030137
TEST=./run_tests.sh

Change-Id: Icd9e7cd26bf7801a4d23cb6bab18336bdb789f83
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3640843
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Auto-Submit: Edward O'Callaghan <quasisec@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
1 file changed