If you want to remove the message from motd without rebooting here is the command to delete the file that has the problem message cached and fully regenerate the motd:
sudo bash -c 'rm /var/lib/update-notifier/fsck-at-reboot && for file in /etc/update-motd.d/*; do $file; done > /var/run/motd' && cat /etc/motd
If you want to remove the message from motd without rebooting here is the command to delete the file that has the problem message cached and fully regenerate the motd:
sudo bash -c 'rm /var/lib/ update- notifier/ fsck-at- reboot && for file in /etc/update- motd.d/ *; do $file; done > /var/run/motd' && cat /etc/motd