Add QQuickItem::geometryChanged as a deprecated method in 5.15.x as it is renamed as QQuickItem::geometryChange() in Qt6

Since in Qt6, QQuickItem::geometryChanged is renamed to QQuickItem::geometryChange() as part of https://github.com/qt/qtdeclarative/commit/9fd4160307ab54b89d0145ebde0a91d293fa95a5

https://doc.qt.io/qt-5/qquickitem.html#geometryChanged (not deprecated)
https://doc-snapshots.qt.io/qt6-dev/qquickitem.html#geometryChange (new at Qt 6.0)

It would be great if it marked as deprecated in next 5.15.x release.