imagemagick7: 7.0.7-27 -> 7.0.7-29

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29/bin/magick-script -h’ got 0 exit code
- ran ‘/nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29/bin/magick-script --help’ got 0 exit code
- ran ‘/nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29/bin/magick -h’ got 0 exit code
- ran ‘/nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29/bin/magick --help’ got 0 exit code
- ran ‘/nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29/bin/magick help’ got 0 exit code
- found 7.0.7-29 with grep in /nix/store/sjpf6fsvmv7aj4x1ngl8ri423cym07cj-imagemagick-7.0.7-29
- directory tree listing: https://gist.github.com/12ed56d2de915ea05dcb89d5486181f8