Update outdated variables

Author: snicoll

README.adoc

@@ -1,5 +1,5 @@
 :spring_version: current
-:spring_boot_version: 2.3.4.RELEASE
+:spring_boot_version: 3.5.10
 :Controller: http://docs.spring.io/spring/docs/{spring_version}/javadoc-api/org/springframework/stereotype/Controller.html
 :DispatcherServlet: http://docs.spring.io/spring/docs/{spring_version}/javadoc-api/org/springframework/web/servlet/DispatcherServlet.html
 :SpringApplication: http://docs.spring.io/spring-boot/docs/{spring_boot_version}/api/org/springframework/boot/SpringApplication.html
@@ -22,7 +22,7 @@ itself and processes those messages.
 
 == What you'll need
 
-:java_version: 1.8
+:java_version: 17
 include::https://raw.githubusercontent.com/spring-guides/getting-started-macros/main/prereq_editor_jdk_buildtools.adoc[]
 * https://cloud.google.com/pubsub/docs/quickstart-console[A Google Cloud Platform project with billing and Pub/Sub enabled]
 * https://cloud.google.com/sdk/[Google Cloud SDK]