fix: Get workspace_id from workflow params

Author: zhanweizhang7

apps/application/flow/step_node/knowledge_write_node/impl/base_knowledge_write_node.py

@@ -146,7 +146,7 @@ def save(self, document_list):
         document_list = serializer.data
 
         knowledge_id = self.workflow_params.get("knowledge_id")
-        workspace_id = "default"
+        workspace_id = self.workflow_params.get("workspace_id")
 
         document_model_list = []
         paragraph_model_list = []