info-overview: Don't show "Firmware Version" row in virtual machines
This value comes from systemd-hostnamed, which harvests it from /sys/class/dmi/id/bios_version, which happens to be empty/invalid in virtual machines (at least KVM powered virtualization).
For this reason, we are better off hiding the "Firmware Version" row when gnome-control-center is running in a VM.
Fixes #2181 (closed)