asio: 1.12.0 -> 1.12.1

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

This update was made based on information from https://repology.org/metapackage/asio/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 1.12.1 with grep in /nix/store/k4y5rhr10i8va653gjnz3ys3i3vj052r-asio-1.12.1
- directory tree listing: https://gist.github.com/c1661a0442144f8187d8ce4d1624b908