Qt Qml Changes of mcpelauncher missing in flathub artifact

QTs QML disk cache is broken in the flatpak client disabling this QT Feature made the problem disappear.

flatpak run --env=QML_DISABLE_DISK_CACHE=1 io.mrarm.mcpelauncher//stable

I will add --env=QML_DISABLE_DISK_CACHE=1 to the manifest, but usually this should not be needed.