alsaPlugins: 1.1.5 -> 1.1.6

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

This update was made based on information from https://repology.org/metapackage/alsa-plugins/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 1.1.6 with grep in /nix/store/cak73591y0nnrnqw3ls6cpg59d73y5s1-alsa-plugins-1.1.6
- directory tree listing: https://gist.github.com/2e3b209cae378a23684ba6f7b276a4b4