Replace expiring certs

[christhompson]

This replaces the following chains whose leafs were set to expire on 2020/03/25:

• wildcard-rsa2048.pem (main wildcard cert)
• wildcard-sha384.pem
• wildcard-sha512.pem
• wildcard-rsa8192.pem

These have been updated on the live site -- this will update the copy in the source to avoid accidentally using the old ones in the future.