MDEV-13589 libmariadbclient18 is broken when using mariadb repo instead of debian's

followup for b5ead3a6

libmariadb3 does not replace 10.1's libmariadbclient18 anymore,
but it still conflicts with it, both install dialog.so

debian/control

@@ -47,7 +47,8 @@ Conflicts: mariadb-galera-server-10.0 (<< 10.0.5),
            mariadb-server-5.1,
            mariadb-server-5.2,
            mariadb-server-5.3,
-           mariadb-server-5.5 (<< 5.5.33)
+           mariadb-server-5.5 (<< 5.5.33),
+           libmariadbclient18 (<< 10.2.0)
 Replaces: libmysqlclient19,
           libmysqlclient20
 Provides: libmysqlclient19,