fix(vectorstores:weaviate|pinecone): do not return error when zero documents are retrieved

[mdelapenya]

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What is this PR doing?

It reverse the logic in Weaviate and Pinecone stores to not return an error if zero docs are retrieved from a SimilaritySearch.

Closes #1065

[FluffyKebab]

@mdelapenya it looks like pinecone also returns error when no documents are found:

langchaingo/vectorstores/pinecone/pinecone.go

Line 172 in 238d1c7

if len(queryResult.Matches) == 0 {

Can you also change the implementation there before we merge?

[mdelapenya]

Sure thing, will add a commit with that ASAP

Thanks for your work here

[mdelapenya]

@FluffyKebab I added the changes to pinecone too. PLMK if you need anything else 🙏

Cheers!

[mdelapenya]

I'm not removing this field although it's not used anymore, but as public API, I thought the deprecation path is the way to go.

In any case, PLMK if I should proceed in any other way