milvus: docstring (#23151)
Added missed docstrings. Format docstrings to the consistent format
(used in the API Reference)
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Co-authored-by: Isaac Francisco <78627776+isahers1@users.noreply.github.com>
Co-authored-by: isaac hershenson <ihershenson@hmc.edu>
Co-authored-by: Erick Friis <erick@langchain.dev>
