Improve Flatpak entry in the Download section
Currently it looks like this:
> or run
$ flatpak install --from https://flathub.org/repo/appstream/org.musescore.MuseScore.flatpakref
This however comes from the time of the old Flathub web interface, and the download link just points to the Flathub homepage.
The web interface not only has pages for all apps, including screenshots, descriptions and package info, but also detailed installation instructions (one must setup Flatpak/Flathub before using it the first time, the page explains this and links to distribution-specific instructions), and command line instructions, should one prefer that. The UX is quite good (try for yourself), so I suggest the entry is changed to the simple following (notice the updated link):