Use PEP 604 syntax wherever possible (#7493)

stdlib/wave.pyi

@@ -1,6 +1,6 @@
 import sys
 from _typeshed import ReadableBuffer, Self
-from typing import IO, Any, BinaryIO, NamedTuple, NoReturn, Union, overload
+from typing import IO, Any, BinaryIO, NamedTuple, NoReturn, overload
 from typing_extensions import Literal
 
 if sys.version_info >= (3, 9):
@@ -8,7 +8,7 @@ if sys.version_info >= (3, 9):
 else:
     __all__ = ["open", "openfp", "Error", "Wave_read", "Wave_write"]
 
-_File = Union[str, IO[bytes]]
+_File = str | IO[bytes]
 
 class Error(Exception): ...