OZG-6592: Remove Groove-base64-decoding-POC

alfa-client/Jenkinsfile.e2e

@@ -839,9 +839,7 @@ String generateNamespace(String bezeichner) {
 }
 
 String decodeString(String encoded) {
-  byte[] decoded = encoded.decodeBase64()
-  return new String(decoded)
-//    return sh (script: "echo -n ${encoded} | base64 --decode", returnStdout: true)
+  return sh (script: "echo -n ${encoded} | base64 --decode", returnStdout: true)
 }
 
 Map getElasticsearchSecret(String namespace) {