seafile-client: 6.1.6 -> 6.1.7

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

This update was made based on information from https://repology.org/metapackage/seafile-client/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 6.1.7 with grep in /nix/store/a366qmps5kxnbp50jw7hyyxx2bizakyl-seafile-client-6.1.7
- directory tree listing: https://gist.github.com/add05f4339b66469b6acbaad439c677f