Update documents in chromaDB VectorStore

[vyeevani]

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This is for use cases that have changing data. For example, casual language modeling for code autocomplete (GitHub CoPilot).

Suppose you make a change in the code that would have impact to something else. You want the vectorstore that would pull this document to reflect that change. For example, you implement some interface on an object in another file. You then go to work on another file while using information of that interfaces implementation.

However, when the chain goes to query the vector-store for similar documents to provide as context, it fails because it's unable to realize that the implementation in the other file is required for this files code.

To address this, the application would have to inform langchain when the user changes the codebase that the code has changed. This involves updating the vector-store to reflect this.

This implementation covers this for chromaDB.

[vyeevani]

I filed #3355 to cover all the other vector stores.