Custom Certificates and CSR available on Business Plan

### Existing documentation URL(s)

- https://developers.cloudflare.com/cloudflare-for-platforms/cloudflare-for-saas/plans/
- https://developers.cloudflare.com/cloudflare-for-platforms/cloudflare-for-saas/security/certificate-management/custom-certificates/certificate-signing-requests/
- https://developers.cloudflare.com/cloudflare-for-platforms/cloudflare-for-saas/security/certificate-management/custom-certificates/

### What changes are you suggesting?

The table in the docs is inconsistent with the pricing page in the dashboard. After upgrading to the Business plan I was able to generate a custom CSR, but the table in the docs says it is only available in Enterprise. CSR support is also vague and differentiating between Custom Certs and Advanced Certs add-on was confusing from the initial api response - `"Access to CSRs has not been granted for this zone. Advanced Certificate Manager or Custom CSR with SSL for SaaS entitlement is required."`

### Additional information

_No response_