Drop unneeded Qt metatype declarations
KCountry & KCountrySubdivision all have a Q_GADGET macro and thus have automatic coverage.
The explicit declaration macros only add costs to all places using the header, where the metatype declaration will be only needed by code using the types in queued connections.
See also end of section here: https://doc.qt.io/qt-6/qmetatype.html#Q_DECLARE_METATYPE