Update the documentation to reflect the fact that .ui.qml files are created on importing and not when exported

Update the documentation to reflect the fact that .ui.qml files are created on importing and not when exported. Currently it says here:

https://doc.qt.io/qtdesignstudio/qtbridge-ps-using.html

Component creates a separate QML file for the selected artboard, group, or layer that contains all the artwork in it, except layers that are set to be skipped or exported as child items.

But this is no longer the case as it is created when it is imported into Qt Design Studio instead.