nix-direnv: use nix (2.4) and remove enableFlakes

Follow-up to #144197 since nixUnstable is no longer needed for flake
support.

pkgs/tools/misc/nix-direnv/default.nix

@@ -2,14 +2,9 @@
 , stdenv
 , fetchFromGitHub
 , gnugrep
-, nixStable
-, nixUnstable
-, enableFlakes ? false
+, nix
+, enableFlakes ? null # deprecated
 }:
-
-let
-  nix = if enableFlakes then nixUnstable else nixStable;
-in
 stdenv.mkDerivation rec {
   pname = "nix-direnv";
   version = "1.5.0";

pkgs/top-level/aliases.nix

@@ -589,6 +589,7 @@ mapAliases ({
   nfsUtils = nfs-utils;  # added 2014-12-06
   nginxUnstable = nginxMainline; # added 2018-04-25
   nilfs_utils = nilfs-utils; # added 2018-04-25
+  nix-direnv-flakes = nix-direnv;
   nix-review = nixpkgs-review; # added 2019-12-22
   nixFlakes = nixStable; # added 2021-05-21
   nmap_graphical = nmap-graphical;  # added 2017-01-19

pkgs/top-level/all-packages.nix

@@ -3336,7 +3336,6 @@ with pkgs;
   nfstrace = callPackage ../tools/networking/nfstrace { };
 
   nix-direnv = callPackage ../tools/misc/nix-direnv { };
-  nix-direnv-flakes = callPackage ../tools/misc/nix-direnv { enableFlakes = true; };
 
   nix-output-monitor = haskell.lib.justStaticExecutables (haskellPackages.nix-output-monitor);