use networkd, it's the future

I turned this on while tryig to make wifi work and although it
didn't have that effect I also haven't subsequently tried turning it off

configuration.nix

@@ -80,6 +80,7 @@ in {
       useDHCP = true;
       hostName = "biscuit";
       networkmanager = { enable = false; };
+      useNetworkd = true;
       inherit (secrets) wireless;
     };