[skip ci]Add comments for upgrade milvus (#10936)

Signed-off-by: yanliang567 <yanliang.qiao@zilliz.com>

tests/python_client/customize/milvus_operator.py

@@ -88,6 +88,13 @@ class MilvusOperator(object):
         cus_res.delete(release_name)
 
     def upgrade(self, release_name, configs, namespace='default'):
+        """
+        Method: patch custom resource object to upgrade milvus
+        Params:
+            release_name: release name of milvus
+            configs: a dict type like configurations to be upgrade milvus
+            namespace: namespace that the milvus is running in
+        """
         if not isinstance(configs, dict):
             log.error("customize configurations must be in dict type")
             return None