picard-tools: 2.18.2 -> 2.18.3

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

This update was made based on information from https://repology.org/metapackage/picard-tools/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 2.18.3 with grep in /nix/store/q67hqz7716nf3c4f8rjmlpf2dqbb06rz-picard-tools-2.18.3
- directory tree listing: https://gist.github.com/6b71ce718f18ef6a48c05457cd0e583b