digikam: 5.8.0 -> 5.9.0

Semi-automatic update generated by https://github.com/ryantm/nix-update tools. 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 5.9.0 with grep in /nix/store/a0lvk4dyi87si7gdyblvh3zs16s0kp76-digikam-5.9.0
- found 5.9.0 in filename of file in /nix/store/a0lvk4dyi87si7gdyblvh3zs16s0kp76-digikam-5.9.0
- directory tree listing: https://gist.github.com/5e9b0273318688eb36b670f51aa482ec