6.9-stable changes

• 27 September 2021: Errata #16: sshd
• 27 September 2021: Errata #17: libressl
• 27 September 2021: Apache2 update
• 30 September 2021: One of the two root certificates used to sign Let's Encrypt certificates expired. This is due to a bug in LibreSSL triggered by Let's Encrypt certificates being signed by two certificates but one expired.