Update link to Apple Root Program Policy

[Preston12321]

Apple now uses markdown in a GitHub repo, and the old link is a landing page that points to the repository.

Note: This page has been retired. The Apple Root Program Policy is now published and maintained on GitHub.

The Apple Root Program Policy is available at https://github.com/apple/apple-root-program/blob/main/policy.md. That document is the authoritative version. This page is no longer updated.

Program requirements, the process for requesting that a Root CA Certificate be included in Apple operating systems, and other Apple Root Program documents are available at https://github.com/apple/apple-root-program.

Questions about the Apple Root Program may be sent to certificate-authority-program@apple.com.