[skip ci] Add line for Jenkinsfile lint (#13027)

Signed-off-by: NJenny Li <jing.li@zilliz.com>

build/ci/jenkins/Nightly.groovy

@@ -7,6 +7,7 @@ String cron_string = BRANCH_NAME == "master" ? "50 22 * * * " : ""
 
 int total_timeout_minutes = 660
 def imageTag=''
+
 pipeline {
     triggers {
         cron """${cron_timezone}