git-radar: 0.5 -> 0.6

Semi-automatic update. 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 0.6 in filename of file in /nix/store/jps6rx12iqgxihhkg2gdi9k29nv1w2kz-git-radar-0.6