Use the new openjpeg shared module

[bochecha]

In addition to the long term benefit of a shared maintenance, this also brings a couple of immediate wins: the latest release has bug and security fixes, and the cmake/cleanup config should result in a slightly faster and smaller build.

This required updating the submodule, and adapting the manifest for the Python 2 rename.

[flathubbot]

Started test build 12341

[flathubbot]

Build 12341 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/11776/net.scribus.Scribus.flatpakref

[jurf]

Cheers, Mathieu!