Remove unsued struct (#9405)

modules/structs/issue.go

@@ -116,9 +116,3 @@ type IssueDeadline struct {
 	// swagger:strfmt date-time
 	Deadline *time.Time `json:"due_date"`
 }
-
-// EditPriorityOption options for updating priority
-type EditPriorityOption struct {
-	// required:true
-	Priority int `json:"priority"`
-}