Update tools/go_back.py

tools/go_back.py

@@ -5,7 +5,7 @@ class GoBackTool(Tool):
     name = "go_back"
     description = "Goes back to the previous page."
     inputs = {}
-    output_type = "None"
+    output_type = "null"
 
     def __init__(self, driver: Any = None, *args, **kwargs):
         super().__init__(*args, **kwargs)