ocamlPackages.ppx_tools_versioned: 5.0.1 -> 5.1

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 5.1 with grep in /nix/store/6bf2nw21lnwsmdy72z7vcwsx7ipvsmmy-ocaml-ppx_tools_versioned-5.1
- directory tree listing: https://gist.github.com/769030f036fe6d5816eb1c77cdd9ecd0