Add Charge version change reasons to seeder

https://eaflood.atlassian.net/browse/WATER-4579

We recently started [seeding the test DB with reference data](#1206). We then [Restructured that seeding to be Knex based](#1230).

We thought we'd covered all reference data with the seeding. But we've just spotted that we missed charge version change reasons (`ChangeReasonModel`).

We're about to add some new unit tests in [Add history attributes to ChargeVersionModel](#1272) that depend on them. So, rather than insert yet more into the DB, this change switches change reasons to be 'reference' based, i.e. tests should select from pre-seeded reasons rather than adding generated ones.