Update Context Retriever Python Client PyPI link

[simba-git]

The original context retriever pypi package was
https://pypi.org/project/context-surfaces/

This still works for backwards compatibility but we prefer
https://pypi.org/project/redis-context-retriever/
Moving forward.

The docs currently have a mix of both, this moves everything to the new one.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Simba Khadder seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

---

^{Security scan by Jit}

[cmilesb]

Thanks @simba-git for doing this! Could you sign our CLA so that we can merge it?