Fixed links that pointed to old docs/source and removed perf page

[acostadon]

Removed perf page and fixed links that pointed to old docs source that are moved to the new docs repository

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[nv-rliu]

Question: did we get rid of all the pages within cugraph and decide to move everything over to docs.rapids.ai during 25.02?

[acostadon]

Question: did we get rid of all the pages within cugraph and decide to move everything over to docs.rapids.ai during 25.02?

There is some developer content remainingin the readme files. I don't think that needs to move over.
I did find 3 more things I need to move over while doing this latest link fixing. I am creating issues for them.

1. move over the GNN readme content to the docs
2. duplicate ( or maybe just move ) the detailed contributing.md page
3. figure out if news should be a thing at the cugraph level. The stuff in there now is useful and needs to be preserved.

[acostadon]

/merge