graphicsmagick: 1.3.28 -> 1.3.29

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

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

These checks were done:

- built on NixOS
- ran ‘/nix/store/j8gk0alkmajz7wsv7wn368blshmk89mk-graphicsmagick-1.3.29/bin/gm help’ got 0 exit code
- ran ‘/nix/store/j8gk0alkmajz7wsv7wn368blshmk89mk-graphicsmagick-1.3.29/bin/GraphicsMagick++-config --version’ and found version 1.3.29
- ran ‘/nix/store/j8gk0alkmajz7wsv7wn368blshmk89mk-graphicsmagick-1.3.29/bin/GraphicsMagick-config --version’ and found version 1.3.29
- ran ‘/nix/store/j8gk0alkmajz7wsv7wn368blshmk89mk-graphicsmagick-1.3.29/bin/GraphicsMagickWand-config --version’ and found version 1.3.29
- found 1.3.29 with grep in /nix/store/j8gk0alkmajz7wsv7wn368blshmk89mk-graphicsmagick-1.3.29
- directory tree listing: https://gist.github.com/014b06393c82c79d1f5dfeea620b71f3