configs/releng/airootfs/etc/systemd/system/getty@tty1.service.d/autologin.conf: update ExecStart

Update the drop-in to more closely match getty@.service of systemd 250.

Use example from https://wiki.archlinux.org/title/getty#Virtual_console
7 jobs for update-getty@.service-drop-in in 5 minutes and 26 seconds (queued for 6 seconds)