qt: fix flickables can no longer be scrolled properly with old Qt (< 6.2.5)

This is for the Qt bug QTBUG-103996. Normally we should not care about this because Qt 6.2.12 is already released open-source, but Qt does not seem to offer these LTS versions pre-built and Ubuntu 20.04 LTS still seems to offer Qt 6.2.4, so it can be useful to have this check for now.

I used 6.2.5 because the patch (https://codereview.qt-project.org/c/qt/qtdeclarative/+/409246) was directed to be cherry picked into the 6.2 LTS branch in May 2022, so I assume 6.2.5 should contain it (which is released in July 2022 for LTS closed source, and July 2023 open source).

This is a regression since !7591 (merged). I'm sorry if this affected anyone, I did not anticipate such a bug in Qt so I did not check it with Qt 6.2 although I use Qt 6.2.4 regularly to test my patches (I try to test with Qt 6.2 if I suspect version of Qt would cause issues to save time).