Upstream Guix upgraded qtserialport to QT@6, which seems to be
incompatible: 50a72a08af37557575199b56bbee9f334d58575a
* nongnu/packages/cad.scm (lightburn)[inputs]: Replace `qtserialport` with
`qtserialport-5`.
* nongnu/packages/cad.scm (lightburn)[inputs]: Rename qtmultimedia to
qtmultimedia-5 due to Guix commit 5f228543394244f479b6a460326fa5f1a4a40998.
Signed-off-by: Jonathan Brielmaier <jonathan.brielmaier@web.de>