community: (milvus) check for num_shards (#20603)
@rgupta2508 I believe this change is necessary following
https://github.com/langchain-ai/langchain/pull/20318 because of how
Milvus handles defaults:
https://github.com/milvus-io/pymilvus/blob/59bf5e811ad56e20946559317fed855330758d9c/pymilvus/client/prepare.py#L82-L85
```python
num_shards = kwargs[next(iter(same_key))]
if not isinstance(num_shards, int):
msg = f"invalid num_shards type, got {type(num_shards)}, expected int"
raise ParamError(message=msg)
req.shards_num = num_shards
```
this way lets Milvus control the default value (instead of maintaining a
separate default in Langchain).
Let me know if I've got this wrong or you feel it's unnecessary. Thanks.
