OZG-5271 OZG-5782 Use Node 20 for Jenkins build

New Jenkins pipeline available, see https://git.ozg-sh.de/ozgcloud-devops/build-management/commit/1eedb4ebed131e475617c2b8482b6f91430d83e7

Jenkinsfile

 pipeline {
     agent {
         node {
-            label 'ozgcloud-jenkins-build-agent-jdk21'
+            label 'ozgcloud-jenkins-build-agent-jdk21-node20'
         }
     }