Use TypeAlias where possible for type aliases (#7630)

stdlib/wave.pyi

@@ -1,14 +1,14 @@
 import sys
 from _typeshed import ReadableBuffer, Self
 from typing import IO, Any, BinaryIO, NamedTuple, NoReturn, overload
-from typing_extensions import Literal
+from typing_extensions import Literal, TypeAlias
 
 if sys.version_info >= (3, 9):
     __all__ = ["open", "Error", "Wave_read", "Wave_write"]
 else:
     __all__ = ["open", "openfp", "Error", "Wave_read", "Wave_write"]
 
-_File = str | IO[bytes]
+_File: TypeAlias = str | IO[bytes]
 
 class Error(Exception): ...