fix(uconsole): align nixos-raspberrypi nixpkgs with nixos-uconsole

Make nixos-raspberrypi follow nixos-uconsole's nixpkgs so the kernel
uses the same nixpkgs that the uconsole Cachix was built with.

flake.nix

@@ -21,6 +21,7 @@
     };
     nixos-raspberrypi = {
       url = "github:nvmd/nixos-raspberrypi/v1.20260517.0";
+      inputs.nixpkgs.follows = "nixos-uconsole/nixpkgs";
     };
     self.submodules = true;
   };