cups-filters: 1.20.1 -> 1.20.2

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

This update was made based on information from https://repology.org/metapackage/cups-filters/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.)
- found 1.20.2 with grep in /nix/store/zbwgknzkhih8rlcizp4s5yi5kinjfv5w-cups-filters-1.20.2
- directory tree listing: https://gist.github.com/a1bcdc4c27ed6a03fa20b81303aaa036