Bump langchain-community>=0.2.9 in test dependencies

[dokterbob]

There's a security vulnerability in the langchain-community < 0.2.9, which is required by langchain, which we're testing against.

Attempting to upgrade langchain to allow patching this runs into a dependency resolution issue with farm-haystack. Langchain requires pydantic > 2 and farm-haystack < 2 only support pydantic < 1.

We should be able to resolve this once farm-haystack >= is released.

Ref:

• Migrate to Pydantic V2 deepset-ai/haystack#5304 (comment)
• https://github.com/Chainlit/chainlit/security/dependabot/55

[dokterbob]

This is solved in main.