gegl_0_3: 0.3.30 -> 0.3.34 (#39241)

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-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/2w7m19f387zkwhxbv6k2p8nrrlwqimpn-gegl-0.3.34/bin/gegl -h’ got 0 exit code
- ran ‘/nix/store/2w7m19f387zkwhxbv6k2p8nrrlwqimpn-gegl-0.3.34/bin/gegl --help’ got 0 exit code
- found 0.3.34 with grep in /nix/store/2w7m19f387zkwhxbv6k2p8nrrlwqimpn-gegl-0.3.34
- directory tree listing: https://gist.github.com/96c792a5cd60943effce7884fc50cc3a