flake: Go back to regular nixos-23.05-small

flake.nix

@@ -1,17 +1,7 @@
 {
   description = "The purely functional package manager";
 
-  # TODO Go back to nixos-23.05-small once
-  # https://github.com/NixOS/nixpkgs/pull/271202 is merged.
-  #
-  # Also, do not grab arbitrary further staging commits. This PR was
-  # carefully made to be based on release-23.05 and just contain
-  # rebuild-causing changes to packages that Nix actually uses.
-  #
-  # Once this is updated to something containing
-  # https://github.com/NixOS/nixpkgs/pull/271423, don't forget
-  # to remove the `nix.checkAllErrors = false;` line in the tests.
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/staging-23.05";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.05-small";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.flake-compat = { url = "github:edolstra/flake-compat"; flake = false; };
   inputs.libgit2 = { url = "github:libgit2/libgit2"; flake = false; };

tests/nixos/default.nix

@@ -10,7 +10,6 @@ let
     hostPkgs = nixpkgsFor.${system}.native;
     defaults = {
       nixpkgs.pkgs = nixpkgsFor.${system}.native;
-      nix.checkAllErrors = false;
     };
     _module.args.nixpkgs = nixpkgs;
   };