user host = (root) NOPASSWD: /sbin/shutdown
user host = (root) NOPASSWD: /sbin/reboot

sudo visudo -f /etc/sudoers.d/shutdown

pkexec visudo

pkexec visudo -f /etc/sudoers.d/shutdown

$ ls -l /etc/sudoers.d/shutdown
-r--r----- 1 root root 86 Jul 16 15:37 /etc/sudoers.d/shutdown

pkexec chown root:root /etc/sudoers.d/shutdown
pkexec chmod 0440 /etc/sudoers.d/shutdown