Remove now unused POM-enrichment for publication to Maven-Central

And downgrade the JDK used in the publishToMaven Jenkins pipeline as we
don't need the latest Java-22/23 features anymore, i.e. the ability to
launch multi-file source-code programs.

Follow-up on
- eclipse-platform#3035

Author: HannesWell

JenkinsJobs/Releng/publishToMaven.jenkinsfile

@@ -10,7 +10,7 @@ pipeline {
 		label 'basic'
 	}
 	tools {
-		jdk 'temurin-jdk23-latest'
+		jdk 'temurin-jdk21-latest'
 		maven 'apache-maven-latest'
 	}
 	environment {
@@ -31,8 +31,7 @@ pipeline {
 					echo "==== Install and run the CBI aggregator ===="
 
 					DIR_AGGREGATOR="${WORKSPACE}/tools/aggregator"
-					MAVEN_PUBLISH_BASE="${WORKSPACE}/git-repo/eclipse.platform.releng/publish-to-maven-central"
-					FILE_SDK_AGGR="${MAVEN_PUBLISH_BASE}/SDK4Mvn.aggr"
+					FILE_SDK_AGGR="${WORKSPACE}/git-repo/eclipse.platform.releng/publish-to-maven-central/SDK4Mvn.aggr"
 
 					# Set whether this is a snapshot build or not
 					if [ "${snapshotOrRelease}" = "-snapshot" ]; then

eclipse.platform.releng/publish-to-maven-central/.classpath

@@ -5,13 +5,7 @@
 	<projects>
 	</projects>
 	<buildSpec>
-		<buildCommand>
-			<name>org.eclipse.jdt.core.javabuilder</name>
-			<arguments>
-			</arguments>
-		</buildCommand>
 	</buildSpec>
 	<natures>
-		<nature>org.eclipse.jdt.core.javanature</nature>
 	</natures>
 </projectDescription>