mail/mutt: Update to 1.13.4

Changelog:

• Fix a potential memory corruption issue when sync'ing imap mailboxes
• Improve the speed of opening mailboxes with large threads (when sorting by thread)
• Change the default of $ssl_force_tls back to unset

PR: 244150
Submitted by: Derek Schrock <dereks@lifeofadishwasher.com> (maintainer)