Use PEP 585 syntax wherever possible (#6717)

stdlib/_typeshed/wsgi.pyi

@@ -3,7 +3,7 @@
 # See the README.md file in this directory for more information.
 
 from sys import _OptExcInfo
-from typing import Any, Callable, Dict, Iterable, Protocol
+from typing import Any, Callable, Iterable, Protocol
 
 # stable
 class StartResponse(Protocol):
@@ -11,7 +11,7 @@ class StartResponse(Protocol):
         self, status: str, headers: list[tuple[str, str]], exc_info: _OptExcInfo | None = ...
     ) -> Callable[[bytes], Any]: ...
 
-WSGIEnvironment = Dict[str, Any]  # stable
+WSGIEnvironment = dict[str, Any]  # stable
 WSGIApplication = Callable[[WSGIEnvironment, StartResponse], Iterable[bytes]]  # stable
 
 # WSGI input streams per PEP 3333, stable