Rollback baseline to support Qt 6.2 on Ubuntu 22.04 LTS

[mappu]

Currently, Miqt generates the package using the Qt 6.4 definitions. The resulting binaries will work with any newer Qt 6 (e.g. latest Qt 6.8), but, using it with older Qt will cause compile-time or link-time failures.

Qt 6.2 was the first LTS release in the Qt 6 series. It is the main/only Qt 6 version available in some older distros such as Ubuntu 22.04. To support running Miqt apps on Ubuntu 22.04, the generated baseline should be rolled back to Qt 6.2.

• What classes would this impact? Is the breakage minor or major?
• Is it still easy to run genbindings?