GeoExporter: Remove the QApplication relic to fix segfault on Alma9 (and because it's not needed!)
The MR removes the relic QApplication to fix a segfault we observed on Lxplus/Alma9.
The QApplication is not needed by GeoExporter.
We need this in 24.0 for debugging the new Detector Description.
The MR is NOT output-changing and no other Athena packages depend on GeoExporter, so it is completely safe to push it to 24.0.