Switch repo promotion to use 8.3.4 version

Signed-off-by: Peter Zhu <zhujiaxi@amazon.com>

Author: peterzhuamazon

jenkins/release-workflows/promote-repos.jenkinsfile

@@ -7,7 +7,7 @@
  * compatible open source license.
  */
 
-lib = library(identifier: 'jenkins@6.4.7', retriever: modernSCM([
+lib = library(identifier: 'jenkins@8.3.4', retriever: modernSCM([
     $class: 'GitSCMSource',
     remote: 'https://github.com/opensearch-project/opensearch-build-libraries.git',
 ]))