Replace old job removal with API endpoint
The lorry-controller-remove-old-jobs script performed a needless amount of API calls for a process that could be performed by a single statement.
There was some reasoning for keeping this external to allow for increased flexibility in implementing the appropriate heuristics for pruning jobs, which could still be performed by interacting with those same API endpoints.
We also pin yoyo-migrations since 9.0.0 breaks the tests/CI.
Edited by Ben Brown