Clean up qt_add_ui() section in "Getting started with CMake"

https://doc.qt.io/qt-6/cmake-get-started.html#building-a-c-gui-application contains a section about qt_add_ui

In specific cases, such as the example below where the include directive uses a relative path, qt_add_ui can be used to generate the ui_calculatorform.h file instead of relying on AUTOUIC. [...]

Problem is that, for beginners, this is completely information overload.

The paragraphs before and after go through the example CMakeLists.txt file one by one. This section is supposed to be a 'footnote/sidenode', but is not marked as such. Furthermore, concepts like 'AUTOUIC' where not even mentioned before, so new users will probably be utterly confused.

I would actually consider removing the whole paragraph from this page. It's enough that the section about qt_add_ui() is mentioned somewhere in 'further reading' .