run STC verification jobs every 4 hours rather than hourly

Change-Id: Ic1a36555c54cc93337fa7af5d5a518c1f584e569
diff --git a/jjb/onos/onos-verify.yaml b/jjb/onos/onos-verify.yaml
index 7fa5a3d..a169264 100644
--- a/jjb/onos/onos-verify.yaml
+++ b/jjb/onos/onos-verify.yaml
@@ -177,8 +177,9 @@
           choosing-strategy: gerrit
           jenkins-ssh-credential: '{jenkins-ssh-credential}'
 
+# runs every 4 hours
     triggers:
-      - timed: '@hourly'
+      - timed: 'H 4,8,12,16,20 * * *'
 
 - release_build_boiler_plate: &release_build_boiler_plate
     name: release_build_boiler_plate