Revert "don't render the delete link when order is complete and it's the last line_item"

This reverts commit a6a57d49445aee8efbde642abdb0ea141a10cc0a.
Revert "don't delete line_item if order is complete and it's the last line item"

This reverts commit 361f23896a893f4ea5990dbac2aff9c48312028a.
user proper validation for deleting last line_item on complete order