[kcms/desktoptheme] Fix removing themes
The current code uses the plasmapkg2 program, which was dropped from libplasma (but may be available from KF5 plasma-framework
Instead use KPackage API, which is nicer than messing with processes anyway
The current code uses the plasmapkg2 program, which was dropped from libplasma (but may be available from KF5 plasma-framework
Instead use KPackage API, which is nicer than messing with processes anyway