libzdb: 3.0 -> 3.1

Semi-automatic update. 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 3.1 with grep in /nix/store/zpsvgnphvh4h494h5ivifrvrb5fjzj0w-libzdb-3.1
- found 3.1 in filename of file in /nix/store/zpsvgnphvh4h494h5ivifrvrb5fjzj0w-libzdb-3.1