graphics/nomacs: update to 3.16
From ChangeLog: https://nomacs.org/nomacs-3-16/
- AVIF support
- CR3, PCX support
- image editing: blurring added
- plugins: adds composite plugin
- windows: new multi-user installer
- adds default system theme
- flatpak: adds plugins
PR: 250757
Submitted by: vidar@karlsen.tech (maintainer)