Mk/bsd.default-versions.mk

• Remove MariaDB 10.0 (removed from ports 2019-04-19)
• Add MariaDB 10.4 (added to ports 2019-06-30)

PR: 240254
Reported by: Dries Michiels <driesm michiels gmail com>
Approved by: portmgr (rene)
Differential Revision: https://reviews.freebsd.org/D21511