Return `429` instead of `302` on Rate Limiter on the raw endpoint

What does this MR do?

Changes HTTP response on the Rate Limiter on the Raw endpoint from 302 to 429. Because of:

• If clients are set to follow HTTP redirects, they will redirect to the "non-raw" Projects::BlobController HTML version of the endpoint, inadvertently leading to more load on our servers instead of less.
• Using the correct status codes makes it easier to track rate limiting events.

Rate Limiter is currently disabled because of this https://gitlab.com/gitlab-org/gitlab-ce/issues/65974#note_203014517

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• [-] 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

Related to #65974 (closed)

Screenshots

When the rate limiter kicks in	When the user clicks on 'redirected'