✏️ Fix typo in `openapi-callbacks.md` (#10673)

docs/en/docs/advanced/openapi-callbacks.md

@@ -38,7 +38,7 @@ This part is pretty normal, most of the code is probably already familiar to you
 !!! tip
     The `callback_url` query parameter uses a Pydantic <a href="https://pydantic-docs.helpmanual.io/usage/types/#urls" class="external-link" target="_blank">URL</a> type.
 
-The only new thing is the `callbacks=messages_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.
+The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.
 
 ## Documenting the callback