gegl_0_3: 0.3.28 -> 0.3.30

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

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

These checks were done:

- built on NixOS
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl -h` got 0 exit code
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl --help` got 0 exit code
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl -V` and found version 0.3.30
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl --version` and found version 0.3.30
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl -h` and found version 0.3.30
- ran `/nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30/bin/gegl --help` and found version 0.3.30
- found 0.3.30 with grep in /nix/store/fn6gs9ss2l0qpxyg3w5y76bx4wlgr9q6-gegl-0.3.30
- directory tree listing: https://gist.github.com/d252f515654f002ddf4d8f3301559e56