fix: release nixpkgs following of mdbook-paisano-preprocessor build

the build it currently not compatible with newer nixpkgs versions; but we also want the config cell to otherwise use current nixpkgs

this commit does remove the nixpkgs folliwing so that the mdbook-paisano-preprocessor build uses the upstream repo's pinned nixpkgs at the expense of not adding a different dependency tree

Author: blaggacao

src/data/flake.lock

@@ -2,12 +2,8 @@
   inputs = {
     # injected (private) inputs
     mdbook-paisano-preprocessor.url = "github:paisano-nix/mdbook-paisano-preprocessor";
-    mdbook-paisano-preprocessor.inputs.nixpkgs.follows = "nixpkgs";
     mdbook-paisano-preprocessor.inputs.nixago.follows = "";
     mdbook-paisano-preprocessor.inputs.devshell.follows = "";
-
-    # injected inputs to override std's defaults
-    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable-small";
   };
   outputs = i: i;
 }