Update articles/upgrading/index.adoc

Co-authored-by: caalador <[email protected]>

Author: tepi

articles/upgrading/index.adoc

@@ -17,9 +17,14 @@ See link:/docs/v24/upgrading/essential-steps[Vaadin 23 to 24 Upgrade Instruction
 
 Many of the breaking changes are needed because of fundamental changes in the Java platform and the major dependencies on which Vaadin relies. This includes the following:
 
+// Allow LTS
+pass:[<!-- vale Vaadin.Abbr = NO -->]
+
 Java 21::
 Vaadin 25 requires Java 21 or later. Java 21 is the latest LTS version of Java. Upgrading to Java 21 might require you to upgrade other dependencies in your application.
 
+pass:[<!-- vale Vaadin.Abbr = YES -->]
+
 Spring Boot 4::
 Vaadin 25 uses the latest Spring Boot 4 and Spring Framework 7 versions. This leads to making breaking changes in Spring-based features, compared to earlier Spring Boot 3.5 and Spring Framework 6 versions. Details can be found in link:https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-4.0-Migration-Guide[Spring Boot 4 Migration Guide].