python-openid: remove, only keep python3-openid

see discussion on
https://github.com/NixOS/nixpkgs/commit/2e41891e6d595b9acf484d7d349b17a7b35b6923

pkgs/development/python-modules/django-allauth/default.nix

@@ -1,5 +1,5 @@
 { stdenv, buildPythonPackage, fetchFromGitHub, requests, requests_oauthlib
-, django, python-openid, mock, coverage }:
+, django, python3-openid, mock, coverage }:
 
 buildPythonPackage rec {
   pname = "django-allauth";
@@ -13,7 +13,7 @@ buildPythonPackage rec {
     sha256 = "1c863cmd521j6cwpyd50jxz5y62fdschrhm15jfqihicyr9imjan";
   };
 
-  propagatedBuildInputs = [ requests requests_oauthlib django python-openid ];
+  propagatedBuildInputs = [ requests requests_oauthlib django python3-openid ];
 
   checkInputs = [ coverage mock ];