gh-137562: Fix github-issue number with deallocated objects in cache

[sergey-miryanov]

@nascheme It seems that #135552 should be referenced in following text:

 * However, since tp_subclasses started being necessary
 * to invalidate caches (e.g. by PyType_Modified), that clearing has created
 * a bug.  If the weakref to the subclass is cleared before a finalizer is
 * called, the cache may not be correctly invalidated.  That can lead to
 * segfaults since the caches can refer to deallocated objects (GH-135552
 * is an example).

Please take a look.

[sergey-miryanov]

This should skip news I believe.