Bug#875027: [libqxt] Future Qt4 removal from Buster

[Thomas Pierson]

Hi Lisandro!

LibQxt is no longer maintained by upstream and I will ask for a removal
as soon as I make Clementine works without it but it takes some work [1].

Thomas

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=875325