docs(cie): fix assumption description to refer to executor association instead of spin()

Signed-off-by: atsushi421 <atsushi.yano.2@tier4.jp>

Author: atsushi421

docs/callback-isolated-executor/integration-guide.md

@@ -65,7 +65,7 @@ For multiple ROS domains, use the `--domains` option:
 ```
 
 !!! warning
-    Due to [autowarefoundation/agnocast#1263](https://github.com/autowarefoundation/agnocast/issues/1263), `CallbackIsolatedAgnocastExecutor` and `agnocast_component_container_cie` assume that all callback groups containing agnocast callbacks are created before `spin()` is called. If an agnocast callback is added to a callback group after `spin()`, the wrong executor type may be selected and the callback will not execute.
+    Due to [autowarefoundation/agnocast#1263](https://github.com/autowarefoundation/agnocast/issues/1263), `CallbackIsolatedAgnocastExecutor` and `agnocast_component_container_cie` assume that all callback groups containing Agnocast callbacks are created before they are associated with the Executor by calling `add_node()` or `add_callback_group()`. If an Agnocast callback is added to a callback group after the callback group is associated with the Executor, the wrong executor type may be selected and the callback will not execute.
 
 ## Step 2: Set Up the Thread Configurator