Rename `/config-names` processing step
the last change of graph steps names in https://github.com/huggingface/datasets-server/issues/1086
next: endpoints and docs :)

**reminder: don't forget to stop the workers before mirgrations!** 
Rename `/config-names` processing step: the last change of graph steps names in https://github.com/huggingface/datasets-server/issues/1086
next: endpoints and docs :)

**reminder: don't forget to stop the workers before mirgrations!** 