Fix missing expose_path for license api paths

What does this MR do?

Part of closing https://gitlab.com/gitlab-org/gitlab-ee/issues/11121. Using api_v4_.*path by itself does not include the relative_url_root, so it will cause 404 problems if not properly exposed.

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

Links

• Part of #11121 (closed)