ci: update `pinecone` test to use serverless (#3127)
### Summary
Closes #3068. Updates the Pinecone connector tests to use serverless
indexes, per the documentation
[here](https://docs.pinecone.io/reference/api/control-plane/create_index).
Also updates the CHANGELOG to mention serverless. Turns out we already
supported it with the client version bump, but it hadn't been tested
yet.
### Testing
See [this CI
job](https://github.com/Unstructured-IO/unstructured/actions/runs/9319836670/job/25655322433?pr=3127)
that passed, running only the Pinecone test.
