The man page for polkitd says:

... Users or administrators should never need to start this daemon as it will be automatically started by dbus-daemon(1) ...

Therefore polkitd will be restarted when dbus service is restarted. Since this service interacts with the desktop manager it is safer to log out of the desktop session, stop xdm service, restart dbus and start xdm again.

It's polkit.service, not polkitd.service.

[tom@archlinux ~]$ cat /usr/lib/systemd/system/polkit.service 
[Unit]
Description=Authorization Manager
Documentation=man:polkit(8)

[Service]
Type=dbus
BusName=org.freedesktop.PolicyKit1
ExecStart=/usr/lib/polkit-1/polkitd --no-debug
[tom@archlinux ~]$ 

Tip: You could have found out with dpkg -L policykit-1 | grep service or even the lists of files of a package on https://packages.ubuntu.com/.

The polkit package in Debian 11 and earlier does not support JavaScript-based rules. Debian maintains a patch that replaces the JS-format rules engine with the older .pkla configuration format.

In this format, the rules would look like this:

[Require authentication for shutdown]
Identity=unix-user:*
Action=org.freedesktop.login1.power-off*;org.freedesktop.login1.reboot*
ResultAny=auth_admin
ResultInactive=auth_admin
ResultActive=auth_admin

See pklocalauthority(8) for the format documentation.

Update

Redhat have changed the RPM dependencies around Polkit. It can now be uninstalled from servers even if something had pulled it in during prior upgrades or installations.

I am now able to uninstall Polkit from servers that other folks built as of CentOS 7.6.

It is still required on Workstations and that appears to be appropriate for desktop usage.