fix(youtube): category set as default when scheduling event

[blackxored]

Category for events was being set to the default of "Entertainment" since it was only updated by the "before go-live" logic.

This moves the update to createBroadcast and re-orders some logic to avoid duplicate requests.

Ideally, we would refactor updateBroadcast to behave in the same way with some diffing and remove all updateCategory calls from the codebase.

ref: https://app.asana.com/0/911512908891105/1202062997993099

[blackxored]

This is a blind change for now as YouTube still has me rate-limited 🔥