multimedia/shotcut-qt6: Update to 25.03.29

Drop local support for Qt5 mlt components being coinstalled. App should
be able to deal with this internally [1] now and there is really no good
reason to have Qt5 mlt7 components coinstalled anymore since kdenlive has
been ported strictly to Qt6.

[1] https://github.com/mltframework/shotcut/commit/017d8b31be696bf3c40f43e08876c83751490131

https://shotcut.org/blog/new-release-250329/