Schema for NUMERIC and geo-spatial array columns shouldn't be optional by default

In PostgresValueConverter#schemaBuilder(Column), the Connect schema is created with optional = true for the NUMERIC, geo-spatial array and BYTEA column types. This shouldn't be done, instead optionality is generically handled in TableSchemaBuilder.

It's no big deal for BYTEA as we only introduce this in the next release, but for NUMERIC and geo-spatial columns a mention in the change notes is warrranted.