remove unnecessary clearing of list

Python/pyarena.c

@@ -159,7 +159,6 @@ PyArena_New()
 void
 PyArena_Free(PyArena *arena)
 {
-    int r;
     assert(arena);
 #if defined(Py_DEBUG)
     /*
@@ -176,12 +175,6 @@ PyArena_Free(PyArena *arena)
     assert(arena->a_objects->ob_refcnt == 1);
     */
 
-    /* Clear all the elements from the list.  This is necessary
-       to guarantee that they will be DECREFed. */
-    r = PyList_SetSlice(arena->a_objects,
-                        0, PyList_GET_SIZE(arena->a_objects), NULL);
-    assert(r == 0);
-    assert(PyList_GET_SIZE(arena->a_objects) == 0);
     Py_DECREF(arena->a_objects);
     free(arena);
 }