python.pkgs.configparser: build with all Python versions

I think the disabled condition was accidentally modified in
ecc939eb19

configparser is a backport of 3.2 functionality. While it is only
intended for Python < 3.2, it works fine with other versions. Even with
pypy, nowadays.

pkgs/development/python-modules/configparser/default.nix

@@ -3,7 +3,6 @@
 buildPythonPackage rec {
   pname = "configparser";
   version = "3.5.0";
-  disabled = isPy3k;
 
   src = fetchPypi {
     inherit pname version;