Change error to warning, to go with dita-ot/dita-ot#2958
Change error to warning, to go with dita-ot/dita-ot#2958

Signed-off-by: Robert D Anderson <4907d442684b61876fae0471c4d2d08024a9ca72@us.ibm.com>

dita-ot/docs,infotexture/docs,infotexture/docs