Change the default incremental_mode to `disabled` due to
https://github.com/scylladb/scylladb/issues/26041 and
https://github.com/scylladb/scylladb/issues/27414
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
(cherry picked from commit c8cff94a5a)