Deprecate KDesktopFile::readDevice()
Since the FSDevice .desktop template hasn't been installed for a long time, this method in KDesktopFile hasn't been useful. The whole FSDesktop concept seems to be redundant nowadays, since CDRom and Floppy drives have been replaced by USB sticks.
See this KF6 taks for more details: https://phabricator.kde.org/T14295#253759