Select the post and schedule it manually.
From the calendar or list view, you can simply select the post that's pending approval, click on Publish Now or Schedule.
Remove that person from the approval process.
Inside the post, go to Approval Process and expand to display all the rounds available. Then simply remove the person you want by clicking on the X next to their profile picture or initials.
You can also replace that person, if necessary, by clicking on Add another approver to this round.
Note: this will only modify the workflow for this particular post and not the template.