Update link to BoltzGen walkthrough in RFdiffusion walkthrough to point to real URL

[tbepler]

This needs to be updated to point to the actual boltzgen walkthrough url.

https://github.com/OpenProteinAI/openprotein-docs/blob/e209bde376c69ef92d68c82868a669b72245b6ff/source/walkthroughs/Protein_protein_binder_design_with_RFdiffusion.ipynb#L2110C8-L2110C80

[timt51]

Completed in #159