Bug#875238: [vmpk] Future Qt4 removal from Buster

[Fabián Rodríguez]

VMPK's author clarified this on their bug tracker:

https://sourceforge.net/p/vmpk/bugs/54/

I've added more information in the VMPK update request bug in Debian here:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870355