nixos/plymouth: multi-user.target wants plymouth-quit-wait.service

This is apparent from the service file directory in plymouth:
├── multi-user.target.wants
│ ├── plymouth-quit.service -> ../plymouth-quit.service
│ └── plymouth-quit-wait.service -> ../plymouth-quit-wait.service

Leaving it unspecified caused gdm-wayland to crash on boot, see #39615.

The change made other display managers not quit plymouth properly however. By
removing "multi-user.target" from `plymouth-quit.after` this is resolved.

Changed files
+2 -1
nixos
modules
system
+2 -1
nixos/modules/system/boot/plymouth.nix
···
systemd.services.plymouth-kexec.wantedBy = [ "kexec.target" ];
systemd.services.plymouth-halt.wantedBy = [ "halt.target" ];
+
systemd.services.plymouth-quit-wait.wantedBy = [ "multi-user.target" ];
systemd.services.plymouth-quit = {
wantedBy = [ "multi-user.target" ];
-
after = [ "display-manager.service" "multi-user.target" ];
+
after = [ "display-manager.service" ];
};
systemd.services.plymouth-poweroff.wantedBy = [ "poweroff.target" ];
systemd.services.plymouth-reboot.wantedBy = [ "reboot.target" ];