(Docs) Make scheduled pipeline timing consistent within the page

What does this MR do?

This file describes the timing for the pipeline schedule cron job twice. It is described once in the "CI/CD" section, and once in the "Cron jobs" section.

The "CI/CD" section has an incorrect default value but reflects the change made on gitlab.com.

The "Cron Jobs" section has a correct default value but incorrectly shows that gitlab.com is using this default.

This MR makes both sections correct and consistent.

An alternative approach would be to remove the "Cron jobs" section entirely so that the information is not duplicated. (If doing this note it is linked to from https://docs.gitlab.com/ee/ci/pipelines/schedules.html and possibly other places). If you'd like me to modify my MR to do this, please let me know.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

This is a documentation-only change.

Security

This is a documentation-only change.