The Qt namespace should be used for types defined in the Qt library,
not for user types.
Pick-to: 6.5
Change-Id: I6df0ca054888f4a65b19a9cb44324321d1dcfad8
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>