Fix appdata for Flathub
Flathub does not accept our https://gitlab.gnome.org/GNOME/pitivi/-/blob/master/data/org.pitivi.Pitivi.appdata.xml.in
argv: b'flatpak run org.freedesktop.appstream-glib validate builddir/*/share/appdata/org.pitivi.Pitivi.appdata.xml'
using PTY: False
builddir/files/share/appdata/org.pitivi.Pitivi.appdata.xml: FAILED:
• style-invalid : <release> description should be prose and not contain hyperlinks [<p>This release adds the following features:</p><ul><li>Replacing the core of Pitivi by GES; 20 thousand lines of code removed</li><li>Porting to GStreamer 1.x</li><li>Porting to GTK+ 3.x</li><li>Replacing GooCanvas by Clutter for the timeline</li><li>An automated UI test suite, with many checks for mission-critical parts</li><li>Fixing hundreds of bugs</li><li>Implementing many new features</li><li>UI polish all over the place</li><li>Refactoring pretty much the entire codebase</li><li>See http://developer.pitivi.org/releases/0-91.html for details</li></ul>]
Edited by Alexandru Băluț