untex: 1.2 -> 1.3

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

This update was made based on information from https://repology.org/metapackage/untex/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 1.3 with grep in /nix/store/vj06kpkl7dm511fy5vnx60dx48n2fhl5-untex-1.3
- directory tree listing: https://gist.github.com/7507195ef91ce9d4ae79a3f80dc453ac