Remove use of leftover CMake flag USE_QT6

[gruenich]

No description provided.

[firewave]

We need to bail out in the CI on unused CMake options (by passing -Werror=dev?). I am not sure if I have not filed a ticket about this yet.

[firewave]

We need to bail out in the CI on unused CMake options (by passing -Werror=dev?). I am not sure if I have not filed a ticket about this yet.

I filed https://trac.cppcheck.net/ticket/14081 about that. But that cannot be easily done right now because of https://trac.cppcheck.net/ticket/14082.

[firewave]

Unfortunately it appears you cannot fail the build on unused manually-specified variables.

[gruenich]

What is the issue with 14082? It behaves as expected.

[firewave]

What is the issue with 14082? It behaves as expected.

It does not matter because it is outside of the scope of this.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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