HSEARCH-3436 Upgrade to version 1.2 of the pipeline helpers

In order to benefit from the latest change, which puts the Maven local
repository outside of the current workspace.

Jenkinsfile

@@ -10,7 +10,7 @@ import groovy.transform.Field
 /*
  * See https://github.com/hibernate/hibernate-jenkins-pipeline-helpers
  */
-@Library('hibernate-jenkins-pipeline-helpers@1.1')
+@Library('hibernate-jenkins-pipeline-helpers@1.2')
 import org.hibernate.jenkins.pipeline.helpers.job.JobHelper
 import org.hibernate.jenkins.pipeline.helpers.alternative.AlternativeMultiMap
 import org.hibernate.jenkins.pipeline.helpers.version.Version