You can cancel a scheduled pause from the Account and the Subscription Details page.
Click on Cancel Pause by clicking on the Options menu of the subscription you'd like to cancel the pause for if you are canceling from the Account or by clicking on the Subscription Actions dropdown if you are on the Subscription Details page. Confirm by clicking Remove Scheduled Pause in the modal.
If you're using the API, to cancel the scheduled pause, pass in a value of 0 as the number of billing cycles to skip with the "Pause Subscription" Endpoint.