fix: clarify day of the week in cron job documentation

The cron scheduling syntax documentation was copied from somewhere else, and included an optional part of the spec (sundays can be referenced as 0 or 7) that is not implemented by kubernetes. This is unnecessarily confusing.

Author: sgoldin

content/en/docs/concepts/workloads/controllers/cron-jobs.md

@@ -55,9 +55,9 @@ The `.spec.schedule` field is required. The value of that field follows the [Cro
 # │ ┌───────────── hour (0 - 23)
 # │ │ ┌───────────── day of the month (1 - 31)
 # │ │ │ ┌───────────── month (1 - 12)
-# │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
-# │ │ │ │ │                                   7 is also Sunday on some systems)
+# │ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
 # │ │ │ │ │                                   OR sun, mon, tue, wed, thu, fri, sat
+# │ │ │ │ │ 
 # │ │ │ │ │
 # * * * * *
 ```