multimedia/shotcut: update to 22.06.23

Summary:
Release notes: https://www.shotcut.org/blog/

Now uses multimedia/mlt7, cmake and more

While here, remove multimedia/webvfx-qt5, as it was abandoned
upstream and only developed with and for shotcut

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D34618