deploy_update_responses-$channel.sh should check that it is not reverting an update in an other channel
When publishing an alpha and stable release at the same time, and
running deploy_update_responses-release.sh and
deploy_update_responses-alpha.sh not in the same order as the releases
were commited to tor-browser-update-responses.git it's possible to
revert the update from the other channel.
The script should check that it's not doing that and display an error otherwise.