PEP 604: Remove some more uses of Union/Optional (#7515)

The following patterns still break mypy:

1. `type[]` at top level fails
2. `tuple[T1, T2]` at top level fails (but `tuple[T1, ...]` is fine)
3. `T1 | Callable[..., T2 | T3]` fails, but only <=3.9

This PR cleans up usage of `Union` and `Optional` outside these patterns.

stdlib/wsgiref/handlers.pyi

@@ -1,6 +1,6 @@
 from abc import abstractmethod
 from types import TracebackType
-from typing import IO, Callable, MutableMapping, Optional
+from typing import IO, Callable, MutableMapping
 
 from .headers import Headers
 from .types import ErrorStream, InputStream, StartResponse, WSGIApplication, WSGIEnvironment
@@ -8,7 +8,7 @@ from .util import FileWrapper
 
 __all__ = ["BaseHandler", "SimpleHandler", "BaseCGIHandler", "CGIHandler", "IISCGIHandler", "read_environ"]
 
-_exc_info = tuple[Optional[type[BaseException]], Optional[BaseException], Optional[TracebackType]]
+_exc_info = tuple[type[BaseException] | None, BaseException | None, TracebackType | None]
 
 def format_date_time(timestamp: float | None) -> str: ...  # undocumented
 def read_environ() -> dict[str, str]: ...