Add some buffer to the connection pools
Add some buffer to the connection pools

`MAX_THREADS` is set to 10 in production. We often exhaust the pool in
the background workers, this shouldn't happen as sidekiq has a
concurrency of 10. Increasing the pool size should give us some extra
room but I'll keep an eye on it.

guidance-guarantee-programme/planner,guidance-guarantee-programme/planner,guidance-guarantee-programme/planner