relative_reference_index in the bed_mesh section is deprecated

[eduhoribe]

Klipper deprecated the relative_reference_index option for the bed_mesh in the version 20230619, details on how to update the configuration are specified here.

After a quick read, my two cents is that we could replace it with the zero_reference_position pointing to one of the bed leveling screws.

[miroan81]

I've just updated to the newest version and this thing popped out. After looking and reading I decided just to comment RRI and leave it like that, did bed mesh few times nothing weird happened, I guess zero_reference_position is not actually needed if everything works ok

[oldcrazyeye]

Updated in the config now, thank you