[DOC] Searching for Thrust documentation on the web shows outdated information

@Kh4ster reports this from frustrated students at a hackathon:

> I'm at a Hackathon and I'm helping people using Thrust, as some point I wanted to show them the doc for thrust::reduce so I asked, just type thrust reduce but the first link is very outdated and not the current CCCL thrust

> Then I said type thrust doc
> Same, very oudated

> Then I said ok type CCCL doc
> First one is the github so not technically the doc and the second one is a specific sub section of the doc

> I think all those things should have either showed first link as being https://nvidia.github.io/cccl/unstable/index.html# or at least, if you click on thrust doc, it should link to https://nvidia.github.io/cccl/unstable/index.html#
> Am I doing/seeing something wrong?

> I was trying to push for thrust and it gave the impression that the documentation was either not their or super hard to find
> Which made convincing them to use Thrust hard