Cleaned up webhook settings on Stripe disconnect
Cleaned up webhook settings on Stripe disconnect

refs https://github.com/TryGhost/Team/issues/1006

These should have been cleaned up previously as they are no longer used
or valid without a Stripe connection.

TryGhost/Ghost,ErisDS/Ghost,ErisDS/Ghost,janvt/Ghost,e10/Ghost,ErisDS/Ghost,e10/Ghost,janvt/Ghost,TryGhost/Ghost,TryGhost/Ghost