fix: wrap fileSystems in mkDefault so disko overrides them

hosts/blade/hardware-configuration.nix

@@ -1,4 +1,4 @@
-# Do not modify this file!  It was generated by ‘nixos-generate-config’
+# Do not modify this file!  It was generated by 'nixos-generate-config'
 # and may be overwritten by future invocations.  Please make changes
 # to /etc/nixos/configuration.nix instead.
 { config, lib, pkgs, modulesPath, ... }:
@@ -13,12 +13,12 @@
   boot.kernelModules = [ "kvm-intel" ];
   boot.extraModulePackages = [ ];
 
-  fileSystems."/" =
+  fileSystems."/" = lib.mkDefault
     { device = "/dev/disk/by-uuid/64882a2d-c966-4fc9-96f0-413c6d835848";
       fsType = "ext4";
     };
 
-  fileSystems."/boot" =
+  fileSystems."/boot" = lib.mkDefault
     { device = "/dev/disk/by-uuid/8381-A6DD";
       fsType = "vfat";
       options = [ "fmask=0022" "dmask=0022" ];