This is a preventive change which will be useful once the rake to
migrate from `spending_proposals` to `budget_investments` is complete
As after running that migration, old `spending_proposal` budgets will
have a newer `id` than the existing budgets. And therefore the last
budget will be one of those migrated from the old `spending_proposal`
model
By ordering by `created_at` and probably updating the `created_at`
attribute in the rake that migrates `spending_proposals` to
`budget_investments`, we will have a coherent order for budgets
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