Doc tx semantics for @TransactionalEventListener after completion phases

This commit improves the Javadoc regarding transactional semantics for
@TransactionalEventListener methods invoked in the AFTER_COMMIT,
AFTER_ROLLBACK, or AFTER_COMPLETION phase. Specifically, the
documentation now points out that interactions with the underlying
transactional resource will not be committed in those phases.

Closes gh-26974

spring-context/src/main/java/org/springframework/context/event/EventListener.java

@@ -83,6 +83,7 @@ import org.springframework.core.annotation.AliasFor;
  * @author Sam Brannen
  * @since 4.2
  * @see EventListenerMethodProcessor
+ * @see org.springframework.transaction.event.TransactionalEventListener
  */
 @Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
 @Retention(RetentionPolicy.RUNTIME)