iso_graphical: fix warning about Plasma 5 desktop module name

nixos/modules/installer/cd-dvd/installation-cd-graphical-kde.nix

···
       autoLogin = true;
     };
 
-    desktopManager.kde5 = {
+    desktopManager.plasma5 = {
       enable = true;
       enableQt4Support = false;
     };
···
   in ''
     mkdir -p /root/Desktop
     ln -sfT ${desktopFile} /root/Desktop/nixos-manual.desktop
-    ln -sfT ${pkgs.kdeApplications.konsole}/share/applications/org.kde.konsole.desktop /root/Desktop/org.kde.konsole.desktop
+    ln -sfT ${pkgs.konsole}/share/applications/org.kde.konsole.desktop /root/Desktop/org.kde.konsole.desktop
     ln -sfT ${pkgs.gparted}/share/applications/gparted.desktop /root/Desktop/gparted.desktop
   '';