Description of problem:
LibreOffice in Fedora 31 and Rawhide now ships 2 different KF5 VCL plugins:
* -kf5 is the GTK3/KF5 VCL plugin that was introduced as a transitional solution,
* -kde5 is the native Qt5/KF5 VCL plugin. (It Obsoletes the old libreoffice-kde4, which is fine.)

This is confusing, because there is actually no such thing as "KDE 5", and users installing libreoffice-kf5 do not expect a mixed GTK3/KF5 interface. In addition, current users of libreoffice-kf5 are not migrated to the native plugin.

Version-Release number of selected component (if applicable):
libreoffice-6.3.0.4-2.fc31

How reproducible:
Always

Steps to Reproduce:
1. Look for available subpackages.

Actual results:
Both -kde5 (Qt5/KF5) and -kf5 (GTK3/KF5).

Expected results:
Only one -kf5 plugin shipping the native Qt5/KF5 VCL plugin. The transitional GTK3/KF5 VCL plugin should be dropped.

Additional info:
I discussed this with Rex Dieter (who originally introduced the GTK3/KF5 VCL plugin as libreoffice-kf5) on IRC. He confirmed that it was not his intention to have the subpackages named this way.

The idea behind naming the GTK3/KF5 VCL plugin libreoffice-kf5 (as opposed to something like libreoffice-gtk3-kf5) in Fedora 30 was to be able to transparently replace it with the native Qt5/KF5 VCL plugin in Fedora 31 without yet another rename.

So we (Rex Dieter) and I propose:
1. dropping (no longer compiling) the GTK3/KF5 VCL plugin and
2. renaming the current -kde5 subpackage (the Qt5/KF5 VCL plugin) to -kf5, conforming to the KDE project's naming guidelines, and ensuring that users of the GTK3/KF5 VCL plugin will be migrated without needing yet another Obsoletes. (Of course, the Obsoletes: libreoffice-kde4 will still be needed.)