graphics/gmic-qt: Update to 3.4.0

Changelog: https://discuss.pixls.us/t/release-of-gmic-3-4/39353
Announcement (in French, English version not yet available):
https://linuxfr.org/news/g-mic-3-4-0-le-traitement-d-images-a-la-fleur-de-l-age