Chore/895 bump dependencies server

[chriswilty]

Description

All backend dependencies upgraded to latest, all vulnerabilities resolved:

Resolves #895

Notes

• langchain upgrade included a few deprecations of functions we were using
• Mocking in our langchain tests needed to be addressed, as the upgraded types were causing compilation errors. Mocking of RetrievalQAChain in particular causes problems, because we are mocking both a static factory method on the class, and methods on an object instance of the class. However, I see that RetrievalQAChain is no longer the recommended way to achieve this call chain: instead we are guided to use the LangChain Expression Language to construct our chains. We will tackle that change in a separate issue, so here I address only the current mock setup.

Checklist

Have you done the following?

• Linked the relevant Issue
• Added tests
• Ensured the workflow steps are passing