This key was introduced in 2008 in some places, but seems it got never
taken into account by the actual kded module loading code when deciding
about the name for the module's D-Bus object path
(at least by what I found in the kdelibs/kded/kdbusaddons repo history).

As any existing kded modules are fine with getting the D-Bus module
name derived from the plugin id (either as set via plugin metadata or
by the binary name), this unused key can be removed again.