Fix GVariant declarations in fu_bluez_device_write
Fix GVariant declarations in fu_bluez_device_write

References to opt_variant and val_variant are sunk in a subsequent
variant creation and consumed by g_dbus_proxy_call_sync. They don't need
to be freed in this context.

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