Remove pre-24.05 workaround for pinning <nixpkgs>

hive.nix

@@ -1,15 +1,18 @@
 let sources = import ./npins;
 in {
-  meta = {
+  meta.nixpkgs = sources.nixpkgs;
-    nixpkgs = sources.nixpkgs;
-  };
 
   defaults = { pkgs, ... }: {
     imports = [
-      ./pinning.nix
       (import "${sources.home-manager}/nixos")
     ];
     deployment.replaceUnknownProfiles = false;
+    
+    # Make <nixpkgs> point systemwide to the pinned nixpkgs above
+    # https://jade.fyi/blog/pinning-nixos-with-npins/
+    nix.settings.experimental-features = "nix-command flakes";
+    nixpkgs.flake.source = sources.nixpkgs;
+    nix.nixPath = ["nixpkgs=flake:nixpkgs"];
   };
 
   tohru = { name, nodes, ... }: {

pinning.nix

@@ -1,23 +0,0 @@
-{ config, pkgs, ... }:
-let sources = import ./npins;
-in {
-  # https://jade.fyi/blog/pinning-nixos-with-npins/
-
-  # We need the flakes experimental feature to do the NIX_PATH thing cleanly
-  # below. Given that this is literally the default config for flake-based
-  # NixOS installations in the upcoming NixOS 24.05, future Nix/Lix releases
-  # will not get away with breaking it.
-  nix.settings.experimental-features = "nix-command flakes";
-
-  # FIXME(24.05 or nixos-unstable): change following two rules to
-  #
-  # nixpkgs.flake.source = sources.nixpkgs;
-  #
-  # which does the exact same thing, using the same machinery as flake configs
-  # do as of 24.05.
-  nix.registry.nixpkgs.to = {
-    type = "path";
-    path = sources.nixpkgs;
-  };
-  nix.nixPath = ["nixpkgs=flake:nixpkgs"];
-}