Fix double free error in fbdev backend

Removed the free(old) call from the _twin_queue_delete function,
consolidating memory deallocation into the _twin_queue_review_order
 function. This change improves memory management and enhances the
maintainability of the code.

The fix was verified using GDB to confirm that old is properly
freed during the execution of free(q) in the
_twin_queue_review_order function. Additionally, AddressSanitizer
was used to confirm the absence of memory leaks and double free
issues.

Author: huaxinliao

src/queue.c

@@ -54,8 +54,6 @@ void _twin_queue_delete(twin_queue_t **head, twin_queue_t *old)
 {
     _twin_queue_remove(head, old);
     old->deleted = true;
-    if (!old->walking)
-        free(old);
 }
 
 twin_queue_t *_twin_queue_set_order(twin_queue_t **head)