Revert "python.pkgs.buildPythonPackage: use distutils-cfg to block downloads, fixes #25428"

This reverts commit b73e3bfafd.

See https://github.com/NixOS/nixpkgs/issues/29103

pkgs/development/interpreters/python/mk-python-derivation.nix

@@ -6,8 +6,6 @@
 , setuptools
 , unzip
 , ensureNewerSourcesHook
-# Prevent impurities by blocking setuptools/easy-install from downloading sdists
-, distutils-cfg
 }:
 
 { name
@@ -62,7 +60,7 @@ python.stdenv.mkDerivation (builtins.removeAttrs attrs ["disabled" "checkInputs"
 
   inherit pythonPath;
 
-  buildInputs = [ distutils-cfg wrapPython ] ++ buildInputs ++ pythonPath
+  buildInputs = [ wrapPython ] ++ buildInputs ++ pythonPath
     ++ [ (ensureNewerSourcesHook { year = "1980"; }) ]
     ++ (lib.optional (lib.hasSuffix "zip" attrs.src.name or "") unzip)
     ++ lib.optionals doCheck checkInputs;

pkgs/top-level/python-packages.nix

@@ -34,7 +34,6 @@ let
   bootstrapped-pip = callPackage ../development/python-modules/bootstrapped-pip { };
 
   mkPythonDerivation = makeOverridable( callPackage ../development/interpreters/python/mk-python-derivation.nix {
-    distutils-cfg = callPackage ../development/python-modules/distutils-cfg { };
   });
 
   # Derivations built with `buildPythonPackage` can already be overriden with `override`, `overrideAttrs`, and `overrideDerivation`.