[Qt-creator] [Dev] Bumping the minimum Qt version required to build Qt Creator

[Eike Ziller]

We plan to bump the minimum Qt version required to build Qt Creator to Qt 6.8.3. (The Qt version that can be used to build user applications is not affected.)
That makes it easier for us to keep the QtTaskTree implementation in sync (until we can completely switch over to the version in Qt),
and allows us to remove a couple of workarounds.

Patch open for comments here:
717575: Bump minimal version to Qt 6.8.3 | https://codereview.qt-project.org/c/qt-creator/qt-creator/+/717575

and some cleanup here
717675: Do some cleanup after the Qt version bump | https://codereview.qt-project.org/c/qt-creator/qt-creator/+/717675

Br, Eike

-- 
Eike Ziller
Principal Software Engineer

The Qt Company GmbH
Erich-Thilo-Str. 10
12489 Berlin, Germany
eike.ziller at qt.io
https://qt.io

Geschäftsführer: Mika Pälsi,
Juha Varelius, Jouni Lintunen
Sitz der Gesellschaft: Berlin, Registergericht: Amtsgericht Charlottenburg, HRB 144331 B