fix: deregister valgrind stack at the end

src/thread/thread.c

@@ -184,6 +184,7 @@ void clear_context(void)
         TAILQ_REMOVE(&head, last, link);
         if (WAS_ALLOCATED(last)) {
             free(last->context.uc_stack.ss_sp);
+            VALGRIND_STACK_DEREGISTER(last->valgrind_id);
         }
         free(last);
     }