Mention _PyTrash_thread_deposit_object and _PyTrash_thread_destroy_chain

Author: sergey-miryanov

Include/cpython/pystate.h

@@ -158,7 +158,10 @@ struct _ts {
     unsigned long native_thread_id;
 
     /* List of objects that still need to be cleaned up, singly linked
-     * via their gc headers' gc_next pointers.  */
+     * via their gc headers' gc_next pointers. The list is populated by
+     * _PyTrash_thread_deposit_object and cleaned up by
+     * _PyTrash_thread_destroy_chain.
+     */
     PyObject *delete_later;
 
     /* Tagged pointer to top-most critical section, or zero if there is no