Cleanup of previous Applet builds

[Alexander.Lohnau at gmx.de]

Hello,

with the accompanying MRs https://invent.kde.org/frameworks/plasma-framework/-/merge_requests/458 a few plugin files got renamed
to ensure that their file name matches the plugin id. Please ensure that the old plugins are deleted,
with kdesrc-build the directory is ~/kde/usr/lib/x86_64-linux-gnu/plugins/plasma/applets/.
After removing this dir, you should install plasma-workspace and optionally kdeplasma-addons (if that is part of your build setup).
Users of package managers will not have any issue, because there old files are deleted.
 
Regards
Alexander