Clean up notebook changelogs

[ChuckHastings]

• A bunch more in the notebooks/ directory: https://github.com/search?q=repo%3Arapidsai%2Fcugraph%20%2Fcuda.*11%2F&type=code

Still pondering.

Edit: FWIW think it would be fine to create a new issue to track updating the benchmarks. Likely the CUDA version is not the only thing that would need an update (other software, hardware, etc.)

Originally posted by @jakirkham in #5162 (comment)

The cugraph notebooks have changelogs at the top of them that include information about hardware and software versions (CUDA versions) that things were tested on. These were added before we had notebook testing as part of our CI process. Now every PR and every release is tested in our CI system. So the information in these changelogs is not as helpful as it formerly was.

Four Options have been discussed:

• the revision block is left unchanged
• drop the "Test Hardware" column which removes references to CUDA versions
• only keep the latest revision line - which should be CUDA 12
• drop the revision block all together