Fix build after https://github.com/NixOS/nixpkgs/pull/56669. Update the
python2 hash and re-add the python2 `futures` dependency. Not sure if
there was a reason for it to be removed in the first place.
The `buildPython*` function computes name from `pname` and `version`.
This change removes `name` attribute from all expressions in
`pkgs/development/python-modules`.
While at it, some other minor changes were made as well, such as
replacing `fetchurl` calls with `fetchPypi`.
