discount: 2.2.3 -> 2.2.3a

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/discount/versions.

These checks were done:

- built on NixOS
- Warning: no binary found that responded to help or version flags. (This warning appears even if the package isn't expected to have binaries.)
- directory tree listing: https://gist.github.com/6518564df191411db8f0004111604991