[Bug]: fail to load partitions with async client

[yanliang567]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

run testcase
async def test_async_milvus_client_load_release_partitions(self):

it reproduces with pymilvus==2.6.0rc123, while it does not reproduce with 2.6.0rc119

Expected Behavior

success

Steps/Code To Reproduce behavior

failed in load partition with async client

Environment details

- Hardware/Softward conditions (OS, CPU, GPU, Memory):
- Method of installation (Docker, or from source):
- Milvus version (v0.3.1, or v0.4.0):
- Milvus configuration (Settings you made in `server_config.yaml`):

Anything else?

stack:

File "/Users/yanliang/fork/milvus/tests/python_client/utils/api_request.py", line 83, in handler
   res = await func(*args, **_kwargs)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/Users/yanliang/fork/milvus/tests/python_client/base/async_milvus_client_wrapper.py", line 98, in load_partitions
   return await self.async_milvus_client.load_partitions(collection_name, partition_names, timeout, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/usr/local/lib/python3.11/site-packages/pymilvus/milvus_client/async_milvus_client.py", line 247, in load_partitions
   await conn.load_partitions(collection_name, partition_names, timeout=timeout, **kwargs)
 File "/usr/local/lib/python3.11/site-packages/pymilvus/client/async_grpc_handler.py", line 846, in load_partitions
   is_refresh=request.is_refresh,
              ^^^^^^^^^^^^^^^^^^
AttributeError: is_refresh

[yanliang567]

/assign @XuanYang-cn