Use PEP 604 syntax wherever possible (#7493)

stdlib/aifc.pyi

@@ -1,7 +1,7 @@
 import sys
 from _typeshed import Self
 from types import TracebackType
-from typing import IO, Any, NamedTuple, Union, overload
+from typing import IO, Any, NamedTuple, overload
 from typing_extensions import Literal
 
 if sys.version_info >= (3, 9):
@@ -19,7 +19,7 @@ class _aifc_params(NamedTuple):
     comptype: bytes
     compname: bytes
 
-_File = Union[str, IO[bytes]]
+_File = str | IO[bytes]
 _Marker = tuple[int, int, bytes]
 
 class Aifc_read: