chore: Update to latest nixos-unstable-small release

cargo-audit has been dropped to fix an issue with libgit2, which should
be fixed in 1-2 weeks or so. Additionally, nvim-base16 has been renamed
to base16-nvim, which is currently only recognized on -small.

flake.nix

@@ -1,6 +1,6 @@
 {
   inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
 
     home-manager = {
       url = "github:nix-community/home-manager";

home/neovim.nix

@@ -57,7 +57,6 @@ in
     rustfmt
     cargo
     cargo-info
-    cargo-audit
     cargo-license
     cargo-feature
     cargo-tarpaulin
@@ -384,7 +383,7 @@ in
       }
       friendly-snippets
       {
-        plugin = nvim-base16;
+        plugin = base16-nvim;
         type = "lua";
         config = "vim.cmd('colorscheme base16-${config.lib.stylix.scheme.slug}')";
       }

modules/packages.nix

@@ -128,7 +128,7 @@
   ];
 
   nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
-    "osu-lazer-bin-2024.130.2"
+    "osu-lazer-bin-2024.131.0"
   ];
 
   nixpkgs.config.permittedInsecurePackages = [