[11.10 backport] Fix approvals section when merge requests disabled

What does this MR do?

This is a 11.10 backport for https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/12070#note_177297004

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

Links

• Closes #11321 (closed)