https://developer.apple.com/documentation/combine/anycancellable
Subscriber implementations can use this type to provide a “cancellation token” that makes it possible for a caller to cancel a publisher, but not to use the Subscription object to request items. An AnyCancellable instance automatically calls cancel() when deinitialized.
deinitで自動的にキャンセルが呼ばれるので、明示的にキャンセルを呼ぶ必要はなさそう