Update screen captures in Qt Installation instructions

The following Qt documentation pages contain screen captures from Qt Online installer:

https://doc.qt.io/qt-6/get-and-install-qt.html

https://doc.qt.io/qt-6/qt-online-installation.html

These should be updated with the screen captures taken from Qt Online Installer 4.7.0. Its beta release is available in download.qt.io: https://download.qt.io/development_releases/online_installers/4.7/

Please note:

• check with the installer team when/where the latest version of the UI is available (contact kamartti )
•  check with release manager tarjasundqvist when the documentation changes can be merged. The estimated Qt Online installer 4.7.0 final release target is on mid-January ... by the end of January.