Add missing SQL upgrade script for NOT NULL on type

`type` column in `Jobsets` is defined as NOT NULL. However, the original upgrade
script adding this column ommited the constraint.

src/sql/upgrade-66.sql

@@ -0,0 +1,2 @@
+update Jobsets set type = 0 where type is null;
+alter table Jobsets alter column type set not null;