Update chat.ts and summarizer.ts

[d3287t328]

https://js.langchain.com/docs/getting-started/install#updating-from-0052## Problem

Describe the purpose of this change. What problem is being solved and why?

Solution

Update deprecated import lines from langchain.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

Check the documentation for correctness.