pdfgrep: 2.0.1 -> 2.1.0

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

This update was made based on information from https://repology.org/metapackage/pdfgrep/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 2.1.0 with grep in /nix/store/myh5qz0s31x6f20qqxnzbjixvsqgm7r1-pdfgrep-2.1.0
- directory tree listing: https://gist.github.com/199c1837bf332973fcb70131751ed26e