Reorder changelog policy rules

What does this MR do?

All the options that require a changelog entry are now listed before what does not need one.

This aims to prevent situations like !17368 (comment 221700267) where a MR with a database migration was proposed without a changelog entry because of

Any change behind a feature flag should not have a changelog entry. The entry should be added in the merge request removing the feature flags.

But several lines later another rule stated

Any change that introduces a database migration must have a changelog entry

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content