pulsebert: use linux 4.19

hosts/pulsebert/configuration.nix

@@ -17,6 +17,7 @@ in {
   # Use the systemd-boot EFI boot loader.
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
+  boot.kernelPackages = pkgs.linuxPackages_4_19;
 
   networking.hostName = "pulsebert"; # Define your hostname.
   # networking.wireless.enable = true;  # Enables wireless support via wpa_supplicant.