mail/postfix: Update to 3.7.0

• Update to 3.7.0
• Correct installation instructions [1]
• Listen on both IPv4 and IPv6 [2]
• Use system-wide CA path [3]
• Correct typo in pkg-message [4]
• Switch to PCRE2 [5]

PR: 261821 [1]
PR: 252872 [2]
PR: 239473 [3]
PR: 261824 [4]
PR: 262100 [5]