[skip ci] Remove nightly trigger (#1775)

Signed-off-by: Nzw <zw@milvus.io>
Co-authored-by: Nzw <zw@milvus.io>

ci/jenkins/Jenkinsfile

@@ -2,7 +2,6 @@
 
 String cron_timezone = "TZ=Asia/Shanghai"
 String cron_string = BRANCH_NAME == "master" ? "H 0 * * * " : ""
-cron_string =  BRANCH_NAME == "0.6.0" ? "H 1 * * * " : cron_string
 
 pipeline {
     agent none