Update app.py

fixed name mismatch

app.py

@@ -66,7 +66,7 @@ agent = CodeAgent(
         final_answer,
         image_generation_tool,
         get_current_time_in_timezone,  # even though it's decorated
-        my_custom_tool                 # same here
+        random_normal_draws                 # same here
     ],
     max_steps=6,
     verbosity_level=1,