[REG 4.9 -> 4.10] Wrong import in project created by wizard

1. Start Creating a new "Qt Quick Application - Empty" using Creator's wizard.
2. On the page "Define Project Details", select the minimum Qt version 5.6.
3. Proceed with defaults until you finished the wizard.
   The created file main.qml start with these lines:

   import QtQuick 2.6
   import QtQuick.Window 2.6
   

   You will not be able to run the project, because Qt 5.6 only contained QtQuick.Window 2.2.

The imports should match what is present in the minimum Qt version. Creator 4.9 did this right.

Found by Squish test tst_qtquick_creation.