gh-151728: Partially revert "Clear the typing caches at interpreter shutdown (GH-154858)" (GH-154992)

Unfortunately, this change causes reference leak tests to fail.

This only reverts the `atexit` registration: it leaves the `_clear_caches` function, to simplify the regrtest utils code a bit.

Author: encukou

Lib/typing.py

@@ -19,7 +19,6 @@
 """
 
 from abc import abstractmethod, ABCMeta
-import atexit
 import collections
 from collections import defaultdict
 import collections.abc
@@ -398,11 +397,6 @@ def _clear_caches():
         cleanup()
 
 
-# Release the LRU caches at shutdown, they otherwise redistribute reference
-# leaks of one extension to types of unrelated ones. See GH-151728.
-atexit.register(_clear_caches)
-
-
 def _tp_cache(func=None, /, *, typed=False):
     """Internal wrapper caching __getitem__ of generic types.