Deletes a subscription. If the subscription requires authentication for deletion, only
the owner of the subscription or the topic's owner can unsubscribe, and an Amazon Web Services signature
is required. If the
Unsubscribe call does not require authentication and
the requester is not the subscription owner, a final cancellation message is delivered
to the endpoint, so that the endpoint owner can easily resubscribe to the topic if the
Unsubscribe request was unintended.
This action is throttled at 100 transactions per second (TPS).