hosts: nixos: porthos: migrate to new host

OVH/Kimsufi are deprecating my current server by the end of the year. So
let's migrate to a new host.

This was more painful than initially planned, OVH introduced a change to
their rescue system which messes with the NixOS installation [1].

In the end I used a kexec image [2] to run the installation.

[1]: https://github.com/NixOS/nix/issues/7790
[2]: https://github.com/nix-community/nixos-images

hosts/nixos/porthos/default.nix

@@ -16,11 +16,5 @@
   # Set your time zone.
   time.timeZone = "Europe/Paris";
 
-  # This value determines the NixOS release from which the default
-  # settings for stateful data, like file locations and database versions
-  # on your system were taken. It‘s perfectly fine and recommended to leave
-  # this value at the release version of the first install of this system.
-  # Before changing this value read the documentation for this option
-  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
-  system.stateVersion = "20.09"; # Did you read the comment?
+  system.stateVersion = "24.05"; # Did you read the comment?
 }