Typo in enum switche_service should be switched_service

Today I received an exception log: Data corrupted at path 'data.object.cancellationDetails.feedback'. Cannot initialize SubscriptionCancellationDetailsFeedback from invalid String value 'switched_service'. I found that the error was caused by this. https://github.com/vapor-community/stripe-kit/blob/0c6ecd9421487daeca5c59b1909cb75b6419cb22/Sources/StripeKit/Billing/Subscriptions/Subscription.swift#L236 Please check the doc https://docs.stripe.com/api/subscriptions/cancel#cancel_subscription-cancellation_details-feedback