Use PEP 604 syntax wherever possible (#7493)

stdlib/http/cookies.pyi

@@ -1,12 +1,12 @@
 import sys
-from typing import Any, Generic, Iterable, Mapping, TypeVar, Union, overload
+from typing import Any, Generic, Iterable, Mapping, TypeVar, overload
 
 if sys.version_info >= (3, 9):
     from types import GenericAlias
 
 __all__ = ["CookieError", "BaseCookie", "SimpleCookie"]
 
-_DataType = Union[str, Mapping[str, Union[str, Morsel[Any]]]]
+_DataType = str | Mapping[str, str | Morsel[Any]]
 _T = TypeVar("_T")
 
 @overload