Update milvus and zilliz docstring (#7216)
Description:
Updating the docstrings for Milvus and Zilliz so that they appear
correctly on https://integrations.langchain.com/vectorstores. No changes
done to code.
Maintainer:
@baskaryan
Signed-off-by: Filip Haltmayer <filip.haltmayer@zilliz.com>
