konversation: Remove maintainer

> Actually, no. I am no longer using IRC and thereby konversation.
https://github.com/NixOS/nixpkgs/pull/180595#issuecomment-1178683153

pkgs/applications/kde/konversation.nix

···
   meta = {
     description = "Integrated IRC client for KDE";
     license = with lib.licenses; [ gpl2 ];
-    maintainers = with lib.maintainers; [ fridh ];
     homepage = "https://konversation.kde.org";
   };
 }