channeldb: TestOutgoingPaymentsMigration is not self-contained against future migrations

channeldb: TestOutgoingPaymentsMigration is not self-contained against future migrations: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). While working on a follow-up migration in channeldb I noticed that TestOutgoingPaymentsMigration (the test for migration 9)…

The task

While working on a follow-up migration in `channeldb` I noticed that `TestOutgoingPaymentsMigration` (the test for migration #9) breaks as soon as anything downstream touches the payment / route decoding path — even if I don't touch migration 9 itself.

Part of FineEnvs/MiMo-V2.6-RL-harbor-code.