Update sync Cron example to be more realistic

What does this MR do?

Customers were misunderstanding these examples to be recommended values. We encountered several customers who had modified their schedules accordingly and were inadvertently running syncs once per minute during the specified hours. It led to performance problems and backed up queues.

Also, several LDAP features were marked Premium only. However, all LDAP features except LDAP group filter are available in Starter and up.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?