Revert "Add monitoring for cron job"

As we resign to develop full-stack solution to monitor cron jobs

This reverts commit 697ce4bf04.

Change-Id: Icab6008011141bb658c836897a05018dd6ce2984

linux/meta/prometheus.yml

@@ -188,15 +188,6 @@ server:
       annotations:
         summary: "Cron process is down"
         description: "The cron process on the {{ $labels.host }} node is down."
-    CronJobFailure:
-      if: >-
-        min(cron_job_status) by (name, host) == 0
-      labels:
-        severity: major
-        service: system
-      annotations:
-        summary: "Cron job failure"
-        description: "The {{ $labels.name }} cron job on the {{ $labels.host }} node failed."
     SshdProcessDown:
       if: >-
         procstat_running{process_name="sshd"} == 0