Update Java version from 8 to 21 in README

Author: yiliuTo

asset-manager/README.md

@@ -3,7 +3,7 @@
 This document serves as a comprehensive workshop guide that will walk you through the process of migrating a Java application to Azure using GitHub Copilot app modernization. The workshop covers assessment, Java/framework upgrades, migration to Azure services, containerization, and deployment.
 
 **What the modernization Process Will Do:**
-The modernization will transform your application from the outdated technologies to a modern Azure-native solution. This includes upgrading from Java 8 to Java 17, migrating from Spring Boot 2.x to 3.x, replacing AWS S3 with Azure Blob Storage, switching from RabbitMQ to Azure Service Bus, migrating to Azure Database for PostgreSQL, implementing managed identity authentication, adding health checks, containerizing the applications, and preparing them for cloud deployment with proper monitoring.
+The modernization will transform your application from the outdated technologies to a modern Azure-native solution. This includes upgrading from Java 8 to Java 21, migrating from Spring Boot 2.x to 3.x, replacing AWS S3 with Azure Blob Storage, switching from RabbitMQ to Azure Service Bus, migrating to Azure Database for PostgreSQL, implementing managed identity authentication, adding health checks, containerizing the applications, and preparing them for cloud deployment with proper monitoring.
 
 ## Table of Contents