trivial: Fix a warning when generating the GtkDoc pages
trivial: Fix a warning when generating the GtkDoc pages

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