Porter's Handbook/Security: Update VuXML content

• Use a valid MITRE CVE instead of outdated CAN
• Remove obsolete MITRE CVE ids, security focus bug id, US Cert id, and US Cert Security alerts
• Update URLs for US Cert vulnerability note and Technical Cyber Security Alert

PR: 277068
Reviewed by: jrm
Sponsored by: https://reviews.freebsd.org/D43992