Bug#919395: Heads up to release team about MariadB 10.3

[Andreas Beckmann <anbe@debian.org>]

Hi,

mariadb-10.3 finally migrated to testing and mariadb-10.1 was just
removed from unstable, so it should leave testing soon as well.

Please schedule the remaining binNMUs s.t. the packages drop the
dependency on the transitional libmariadbclient18 package.

Thanks

Andreas