Add a warning explaining that events consumed by an until clause should be excluded by a listen task's output, following @fjtirado's comment

Signed-off-by: Charles d'Avernas <charles.davernas@neuroglia.io>

Author: cdavernas

dsl-reference.md

@@ -661,6 +661,10 @@ Provides a mechanism for workflows to await and react to external events, enabli
 > [!NOTE]
 > When `foreach` is set, the configured operations for a [events](https://cloudevents.io/) must complete before moving on to the next one. As a result, consumed [events](https://cloudevents.io/) should be stored in a First-In-First-Out (FIFO) queue while awaiting iteration.
 
+> [!WARNING]
+> [Events](https://cloudevents.io/) consumed by an `until` clause should not be included in the task's output. These [events](https://cloudevents.io/) are used solely to determine when the until condition has been met, and they do not contribute to the result or data produced by the task itself
+
+
 ##### Examples
 
 ```yaml