Run verification builds on Java 21

Prereq for
eclipse-platform/eclipse.platform.releng.aggregator#2654

Author: akurtakov

.github/workflows/maven.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [ '17' ]
+        java: [ '21' ]
         config: 
           - { name: Linux, os: ubuntu-latest, native: gtk.linux.x86_64 }
           - { name: Windows, os: windows-latest, native: win32.win32.x86_64 }

Jenkinsfile

@@ -87,7 +87,7 @@ pipeline {
 		label 'ubuntu-latest'
 	}
 	tools {
-		jdk 'temurin-jdk17-latest'
+		jdk 'temurin-jdk21-latest'
 		maven 'apache-maven-latest'
 	}
 	environment {