stdlib: audit more callback annotations (#8209)

stdlib/atexit.pyi

@@ -1,5 +1,5 @@
 from collections.abc import Callable
-from typing import Any, TypeVar
+from typing import TypeVar
 from typing_extensions import ParamSpec
 
 _T = TypeVar("_T")
@@ -9,4 +9,4 @@ def _clear() -> None: ...
 def _ncallbacks() -> int: ...
 def _run_exitfuncs() -> None: ...
 def register(func: Callable[_P, _T], *args: _P.args, **kwargs: _P.kwargs) -> Callable[_P, _T]: ...
-def unregister(func: Callable[..., Any]) -> None: ...
+def unregister(func: Callable[..., object]) -> None: ...