chore: require minimum httpcore with security fix for h11

[danielfcollier]

Summary

The httpcore subdependency h11 has a security fix for the critical security issue that requires the minimum version 1.0.9.

References:

• https://osv.dev/vulnerability/GHSA-vqfr-h8mv-ghfj
• https://github.com/encode/httpcore/releases/tag/1.0.9

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[davidrogger]

Nice work!

[lovelydinosaur]

Duplicate of #3560

[BryceLohr]

Duplicate of #3560

I'm trying to understand what this means: are you saying that httpx will not update its dependency to resolve this security issue? Or am I misunderstanding this?

[zanieb]

Yes there's no need to change the minimum required version for users to receive the security fix as was discussed at length in #3564 (comment)