Fix approvals section when merge requests disabled

What does this MR do?

This fixes a bug where the project edit page was fetching approval settings when merge requests were disabled.

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

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Links

• Closes #11321 (closed)