Fix behaviour of attachment table for purchase orders (#3127)

- Refresh table, rather than reloading page!

(cherry picked from commit 141c2370e3a19526def9bfcd7ccac50e60e1684a)

InvenTree/order/templates/order/purchase_order_detail.html

@@ -135,7 +135,7 @@
             },
             label: 'attachment',
             success: function(data, status, xhr) {
-                location.reload();
+                $('#attachment-table').bootstrapTable('refresh');
             }
         }
     );