Finish removing deprecated code.

Aside from -Wsuggest-override errors in auto-generated Qt and Taglib
code, JuK compiles without warning again.
2 jobs for master in 7 minutes and 9 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #7199
flatpak
flatpak

00:07:06

passed #7198
linux kf5-qt5 qt5.10

00:07:08

2.0%