bftpd: 4.8 -> 4.9

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

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

These checks were done:

- built on NixOS
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd -h` got 0 exit code
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd --help` got 0 exit code
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd -v` and found version 4.9
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd --version` and found version 4.9
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd -h` and found version 4.9
- ran `/nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9/bin/bftpd --help` and found version 4.9
- found 4.9 with grep in /nix/store/22swhqg3b1j8jxnlnndb9d4rhx5ajaam-bftpd-4.9
- directory tree listing: https://gist.github.com/f0a3568c5073cae5ff7e99964b767161