nnn: 1.7 -> 1.8 (#40083)

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/ry70cgfhdagmk70n6wn6968mqg8h3js8-nnn-1.8/bin/nlay -h’ got 0 exit code
- ran ‘/nix/store/ry70cgfhdagmk70n6wn6968mqg8h3js8-nnn-1.8/bin/nlay --help’ got 0 exit code
- ran ‘/nix/store/ry70cgfhdagmk70n6wn6968mqg8h3js8-nnn-1.8/bin/nlay help’ got 0 exit code
- found 1.8 with grep in /nix/store/ry70cgfhdagmk70n6wn6968mqg8h3js8-nnn-1.8
- directory tree listing: https://gist.github.com/261e9182ffd2085e4d82ca4daefdcee6