trivial: Add some documentation for the ApprovedFirmware config key
trivial: Add some documentation for the ApprovedFirmware config key

hughsie/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,hughsie/fwupd,hughsie/fwupd,fwupd/fwupd,fwupd/fwupd