update cron every 30'

Jenkinsfile

@@ -39,7 +39,7 @@ pipeline {
 
     triggers {
 //     every fifteen minutes (perhaps at :07, :22, :37, :52)
-       cron('H/15 * * * *')
+       cron('H/30 * * * *')
 //     once in every two hours slot between 9 AM and 5 PM every weekday (perhaps at 10:38 AM, 12:38 PM, 2:38 PM, 4:38 PM)
 //       cron('H H(9-16)/6 * * 1-5')
     }