Plugin makes dolphin crash

Having this installed as phonon backend makes dolphin crash when previewing video files. This is of course an upstream bug (which has been reported and unfixed for over a year), but the issue is that this is being installed as default phonon backend for new installs (since it comes before phonon-vlc alphabetically), and users are wrongly reporting the crashes upstream to KDE.

Until this is better maintained upstream, we should either drop the package or stop providing phonon-backend so it stops being installed as default provider.