Package must port away from KDELibs4Support

[a17r]

• Porting away from KDE4 Support is necessary to be in a good place for Qt6/KF6
• Package will benefit from a much leaner dependency set

Porting notes: https://community.kde.org/Frameworks/Porting_Notes Porting scripts: https://invent.kde.org/sdk/kde-dev-scripts

[a17r]

Maybe @valeth is still interested to do some work there? :)