pgroonga: 2.0.5 -> 2.0.6 (#40646)

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

This update was made based on information from https://repology.org/metapackage/pgroonga/versions.

These checks were done:

- built on NixOS

- 0 of 0 passed binary check by having a zero exit code.
- 0 of 0 passed binary check by having the new version present in output.
- found 2.0.6 with grep in /nix/store/nh4mqn37kx82q7l5fm6anycaw8iz7b8n-pgroonga-2.0.6
- directory tree listing: https://gist.github.com/14e8971d0a27517ef320553ce1e8d33c
- du listing: https://gist.github.com/c1f25e2851a59216d5fa9f88b6477927