fix List type parsing

Author: streamnsight

langchain_mcp_adapters/tools.py

@@ -168,7 +168,7 @@ def _parse_field(props):
                 return Literal[tuple(props['enum'])]
             if props['type'] == 'array':
                 items = props['items']
-                return List[tuple(_parse_field(items))]
+                return List[_parse_field(items)]
             else:
                 return type_map.get(props['type'], dict)