Use hut substituter in all nodes

Reviewed-by: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>

m/fox/configuration.nix

@@ -8,6 +8,7 @@
     ../module/emulation.nix
     ../module/nvidia.nix
     ../module/slurm-client.nix
+    ../module/hut-substituter.nix
     ./wireguard.nix
   ];
 
@@ -62,12 +63,6 @@
     interfaces.enp1s0f0np0.useDHCP = true;
   };
 
-  # Use hut for cache
-  nix.settings = {
-    extra-substituters = [ "https://jungle.bsc.es/cache" ];
-    extra-trusted-public-keys = [ "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" ];
-  };
-
   # Recommended for new graphics cards
   hardware.nvidia.open = true;