Add admin option to disable manual billing for a team

[knolleary]

Putting a team into manual billing mode is currently a one-way street in the UI.

Taking a team out of manual billing mode requires a database poke. This means only those with direct access to the production database can do so and it isn't something our customer success folk can do directly.

Making the existing button a toggle, with the backend api to handle it, is a quick piece of work and will unblock this workflow and take me off the critical path for this task.