fix: incorrect 24 hour format comment example (#15649)

### What?

The code comment for type
`CollectionConfig.versions.drafts.schedulePublish.timeFormat` suggests
using 'hh:mm' for a 24 hour clock format. I changed this comment to
instead suggest 'HH:mm'.

### Why?

The lowercase 'hh' makes a 12 hour format, not the suggested 24 hour
format.

### How?

I replaced the comment to suggest using uppercase 'HH' instead.

```diff
-   * @example 'hh:mm' will give a 24 hour clock
+   * @example 'HH:mm' will give a 24 hour clock
 ```

Co-authored-by: Paul Popus <paul@payloadcms.com>