The former is dead, the latter is the new name. See:
http://cgit.freedesktop.org/systemd/systemd/commit/?id=
b2c9cbafb8b1a2742978e1faf37fbb3cf4fb5d44
https://fedoraproject.org/wiki/Features/DisplayManagerRework
[Unit]
Description=Restore /run/initramfs
Documentation=man:dracut-shutdown.service(8)
-After=getty@tty1.service prefdm.service
+After=getty@tty1.service display-manager.service
Before=systemd-reboot.service shutdown.target
DefaultDependencies=no
ConditionPathExists=/run/initramfs/.need_shutdown