Make cuid columns 30 characters wide

[sktt]

Missed some spots from setting id columns to 30 characters. (https://github.com/prisma/prisma-engines/issues/878)

We learned this the hard way (production db) and it was quite hard to debug since the error message we got was Error: The provided value for the column is too long for the column's type. Column: <unknown>.

The column was actually one of a join table for a many-to-many relation.