flash-installer: disable state-version

We cannot have vars in here because it breaks:

```
  clan flash write --flake https://git.clan.lol/clan/clan-core/archive/main.tar.gz   --ssh-pubkey $HOME/.ssh/id_ed25519.pub   --keymap us   --language en_US.UTF-8   --disk main /dev/sdb   flash-installer
```

templates/machine/flash-installer/configuration.nix

@@ -10,6 +10,9 @@
     clan-core.nixosModules.installer
   ];
 
+  # We don't need state-version in a live installer
+  clan.core.settings.state-version.enable = false;
+
   clan.core.deployment.requireExplicitUpdate = true;
 
   nixpkgs.pkgs = inputs.nixpkgs.legacyPackages.x86_64-linux;