Deprecate KProtocolInfo::slaveHandlesNotify()
The only known user (kio_desktop) lost the flag some years ago by accident, (plasma/plasma-workspace@42efaf44) and the code complementing it also changed, breaking the intent.
See https://bugs.kde.org/show_bug.cgi?id=461793
Until someone comes up with a fix for that bug which then also needs again a respective counterpart in KIO, this feature can be deprecated.
Edited by Friedrich W. H. Kossebau