HSEARCH-4155 Update an obsolete comment in PojoIndexingPlanImpl

Signed-off-by: Yoann Rodière <yoann@hibernate.org>

mapper/pojo-base/src/main/java/org/hibernate/search/mapper/pojo/work/impl/PojoIndexingPlanImpl.java

@@ -205,7 +205,11 @@ private PojoRuntimeIntrospector getIntrospector() {
 	}
 
 	private void updateBecauseOfContained(Object containingEntity) {
-		// TODO ignore the event when containingEntity has provided IDs
+		// Note this method won't work when using provided identifiers
+		// Fortunately, all platforms relying on provided identifiers (Infinispan)
+		// also disable reindexing of other entities on updates,
+		// so they won't ever call this method.
+
 		PojoRawTypeIdentifier<?> typeIdentifier = getIntrospector().detectEntityType( containingEntity );
 		if ( typeIdentifier == null ) {
 			throw new AssertionFailure(