[DOC]: Update README for the latest state of the notebooks

[acostadon]

How would you describe the priority of this documentation request

High

Please provide a link or source to the relevant docs

https://github.com/rapidsai/cugraph/blob/main/notebooks/README.md

Describe the problems in the documentation

Needs to reflect recent notebook changes and additions

(Optional) Propose a correction

No response

Code of Conduct

• I agree to follow cuGraph's Code of Conduct
• I have searched the open documentation issues and have found no duplicates for this bug report