desktop: Replace KDE cherry-picking with meta packages

The additional packages introduced by this are cervisia, dragonplayer, juk, konqueror, perl-doc. Excluding those does not justify maintaining this list and trying to understand Debian KDE packaging again with every release upgrade.

desktop/files/apt-pin

+Package: plasma-nm network-manager cups-daemon plasma-discover
+Pin: origin *
+Pin-Priority: -1