Order budget headings by id
Order budget headings by id

To maintain order after editing a heading’s name

We should probably add timestamps to `groups` and `headings` and order
by `created_at` instead

Could have done it in a separate PR, but gotta keep moving to other
priority issues. Creating issue for timestamps to do correctly and with
tests :relieved:

AyuntamientoMadrid/consul,AyuntamientoMadrid/consul,AyuntamientoMadrid/consul,AyuntamientoMadrid/consul