[flake-parts] Use git-hooks as non-flake input

[srid]

The flake-parts template currently suggests using it as a flake input:

git-hooks.nix/template/flake.nix

Lines 6 to 7 in cd1af27

	git-hooks-nix.inputs.nixpkgs.follows = "nixpkgs";
	git-hooks-nix.url = "github:cachix/git-hooks.nix";

This brings in a bunch of transitive inputs that the user does not strictly need, forcing setting up of follows like:

    git-hooks.inputs = {
      nixpkgs.follows = "nixpkgs";
      nixpkgs-stable.follows = "nixpkgs";
    };
    gitignore.follows = "git-hooks/gitignore";
    gitignore.inputs.nixpkgs.follows = "nixpkgs";
    gitignore.inputs.flake-compat = { };

Therefore, should we just change the template to reference git-hooks as a non-flake input? viz.:

    git-hooks.url = "github:cachix/git-hooks.nix";
    git-hooks.flake = false;

    ...

    # In imports
    (inputs.git-hooks + /flake-module.nix)