fldigi: 3.23.15 -> 4.0.16

Semi-automatic update. These checks were done:

- built on NixOS
- ran `/nix/store/vxx260nm7dk471pgh1090pp9xlm53hbs-fldigi-4.0.16/bin/fldigi --help` got 0 exit code
- ran `/nix/store/vxx260nm7dk471pgh1090pp9xlm53hbs-fldigi-4.0.16/bin/fldigi --version` and found version 4.0.16
- ran `/nix/store/vxx260nm7dk471pgh1090pp9xlm53hbs-fldigi-4.0.16/bin/flarq --help` got 0 exit code
- found 4.0.16 with grep in /nix/store/vxx260nm7dk471pgh1090pp9xlm53hbs-fldigi-4.0.16
- found 4.0.16 in filename of file in /nix/store/vxx260nm7dk471pgh1090pp9xlm53hbs-fldigi-4.0.16