使zhipuai变为非必要依赖(close #1369)

server/model_workers/zhipu.py

@@ -1,4 +1,3 @@
-import zhipuai
 from server.model_workers.base import ApiModelWorker
 from fastchat import conversation as conv
 import sys
@@ -37,6 +36,7 @@ class ChatGLMWorker(ApiModelWorker):
     def generate_stream_gate(self, params):
         # TODO: 支持stream参数，维护request_id，传过来的prompt也有问题
         from server.utils import get_model_worker_config
+        import zhipuai
 
         super().generate_stream_gate(params)
         zhipuai.api_key = get_model_worker_config("chatglm-api").get("api_key")