Increase export rate limit to match import rate limit

What does this MR do?

Fixes a bug from !31719 (merged) which removed the project scope from the rate limit, but did not change the rate limit at the same time, so this is now very restrictive.

Update these rate limits to be 30 every 5 mins (the same as import). Also update all the group export endpoints, as they should have the same limiting.

This is part of https://gitlab.com/gitlab-org/gitlab/-/issues/212707

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability 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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• ~~Label as security and @ mention @gitlab-com/gl-security/appsec~~
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team