commonsIo: 2.4 -> 2.6

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 2.6 with grep in /nix/store/5yl4dj084qj2x6xawqpbgs9bmlgxjjkb-commons-io-2.6
- found 2.6 in filename of file in /nix/store/5yl4dj084qj2x6xawqpbgs9bmlgxjjkb-commons-io-2.6
- directory tree listing: https://gist.github.com/a62494f31c4e13128a99cb347f615952