cups-filters: 1.20.0 -> 1.20.1

Semi-automatic update generated by https://github.com/ryantm/nix-update tools. 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 1.20.1 with grep in /nix/store/233chsllrfymrvizn74nf8sav0r0llrb-cups-filters-1.20.1