qproperty-without-notify should not warn for properties in a Q_GADGET class
qproperty-without-notify warns about properties that have no NOTIFY signal. Anyhow, value classes using Q_GADGET cannot really have NOTIFY signals in the first place, but can have properties. The check shouldn't therefore warn for Q_PROPERTY in a Q_GADGET class.
See also https://lists.qt-project.org/pipermail/development/2024-January/044884.html