backend: Remove unused BVW_INFO_COVER
It was probably going to be used to display embedded album art in the nautilus properties, but those properties were 1) ported to GstDiscoverer and 2) migrated to nautilus itself.
It was probably going to be used to display embedded album art in the nautilus properties, but those properties were 1) ported to GstDiscoverer and 2) migrated to nautilus itself.