SONARJAVA-4881 Update S2230 to only target Spring <= 5

rules/S2230/java/rule.adoc

@@ -1,9 +1,14 @@
 == Why is this an issue?
 
-Marking a non-public method `@Async` or `@Transactional` is misleading because Spring does not recognize non-public methods, and so makes no provision for their proper invocation.
+Marking a non-public method `@Async` or `@Transactional` is misleading because, up to version 5, Spring does not recognize non-public methods, and so makes no provision for their proper invocation.
 Nor does Spring make provision for the methods invoked by the method it called.
+Since Spring 6, protected and package-private methods can be handled, but the issue remains for private methods.
 
-Therefore marking a private method, for instance, @Transactional can only result in a runtime error or exception if the method is annotated as @Transactional.
+Therefore, marking a private method, for instance, @Transactional gives a false sense of security, and can lead to incorrect assumptions and potential bugs.
+
+== Exceptions
+
+The rule targets all non-public methods for project using Spring up to Spring 5, but only private methods for Spring 6 because Spring 6 takes into account all non-private methods.
 
 == How to fix it
 
@@ -39,6 +44,7 @@ public Future<String> asyncMethodWithReturnType() { // Compliant
 
 - https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/scheduling/annotation/Async.html[Spring Framework API - Annotation Interface Async]
 - https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/transaction/annotation/Transactional.html[Spring Framework API - Annotation Interface Transactional]
+- https://docs.spring.io/spring-framework/reference/6.2.6/data-access/transaction/declarative/annotations.html#transaction-declarative-annotations-method-visibility[Method visibility and @Transactional in proxy mode]
 
 === Articles & blog posts