[FR] - Update Proposal Script to Babbage for private testnets

**Internal/External**
*External*  

**Area**
*Other*  

**Describe the feature you'd like**
It would be great to have an additional update script, that is update-6.sh, in ``scripts/byron-to-alonzo`` which does the transition to Babbage era.

This is related to this issue: https://github.com/input-output-hk/cardano-node/issues/4167