fox_1_6: 1.6.56 -> 1.6.57

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/0d83j376zvh006b5slmgdx86bcm3dxkm-fox-1.6.57/bin/reswrap -h’ got 0 exit code
- ran ‘/nix/store/0d83j376zvh006b5slmgdx86bcm3dxkm-fox-1.6.57/bin/reswrap --help’ got 0 exit code
- ran ‘/nix/store/0d83j376zvh006b5slmgdx86bcm3dxkm-fox-1.6.57/bin/fox-config --version’ and found version 1.6.57
- found 1.6.57 with grep in /nix/store/0d83j376zvh006b5slmgdx86bcm3dxkm-fox-1.6.57
- directory tree listing: https://gist.github.com/baa2d8696211116ff0be92b664965741