You can remove runs from automations that have a scheduled run at a future date or are recurring. 

To remove a run from an automation with one or more scheduled runs, hover over the run and click the trash can icon that appears.

To remove a recurrence from an automation with a recurring schedule, hover over the run that you want to remove and click the trash can icon that appears.

To remove an entire recurrence from an automation with a recurring schedule, click the trash can icon that appears next to the schedule details.