README report that Creo 9 is the one supported and tested, but linked guidelines suggest that Creo <= 8 should be used

[traversaro]

The README report that Creo 9 is used, but if one follows in the next section the suggested guidelines at https://github.com/icub-tech-iit/cad-libraries/wiki/Prepare-PTC-Creo-Mechanism-for-URDF, it is explicitly reported that:

Warning: the following procedure works only with MATLAB <= R2017b and Creo <= 8.

While I guess this is already tracked in https://github.com/icub-tech-iit/cad-libraries/issues/174, for someone new to creo2urdf it is not easy to understand that removing the reference to Creo <= 8 is a todo. Could it make sense to add a notice before the link on the creo2urdf to ignore the remarks about the Creo version?

fyi @davidebarbone @mfussi66 @Nicogene