fix(vector_stores): Unexpected return value on MilvusDB

[Zynoo71]

Description

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Fixes # (issue)

Type of change

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• [x] Bug fix (non-breaking change which fixes an issue)

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Maintainer Checklist

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[Zynoo71]

Bug Reproduction

`

use MilvusDB as vector_store

memory = Memory.from_config(config)
memory.add(
    messages="i don't like curry now",
    user_id="default_user",
)
print(memory.get_all(user_id="default_user"))

`

I checked the function declaration, MilvusDB.list should return List[OutputData] but now return [ List[OutputData] ]

[parshvadaftari]

@Zynoo71 can you resolve merge conflicts? And can you check for the other vectorstore the output is consistent throughout the vectorstores and this is what it's supposed to be.

[parshvadaftari]

@Zynoo71 can you share the output for all the memory functions? Thanks