Fix group usage quota menu item

What does this MR do?

During gitlab-ee!13294 development the Usage quota menu item was wrongly placed under the if @group.feature_available?(:audit_events) condition.

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.
• [-] Tested in all supported browsers