Indeterminacy in Chunk Fetching

[FraserLee]

The result we get from pinecone at https://github.com/StampyAI/stampy-chat/blob/main/api/get_blocks.py#L81 appears to probably be deterministic, but somewhere in the de-duplication and source merging between that and the end of the function we're getting some indeterminacy. Can be demonstrated with the query "Give me a random number", k = 10.

The results from this function should be deterministic.