milvus secure check fix (#1305)

Co-authored-by: jyong <jyong@dify.ai>

api/core/index/vector_index/milvus_vector_index.py

     port: int
     user: str
     password: str
-    secure: bool
+    secure: bool = False
     batch_size: int = 100
 
     @root_validator()
             raise ValueError("config MILVUS_HOST is required")
         if not values['port']:
             raise ValueError("config MILVUS_PORT is required")
-        if not values['secure']:
-            raise ValueError("config MILVUS_SECURE is required")
         if not values['user']:
             raise ValueError("config MILVUS_USER is required")
         if not values['password']: