How we can delete a goal plan from Employee

Dear Experts - Is there a possibility to remove/delete a goal plan from an employee once it's assigned? 

Gone through the CC post but unable to find any solution for us Delete all assignee is not showing.

After clicking on Manage Assignees also delete button is not showing.

Please suggest some steps to delete Goal plan from all assignees.

Note: Goals are included in the Performance Document and the document is in progress or completed

Regards,

Glorina