improve typing for teardown_request

Author: pcorpet

CHANGES.rst

@@ -5,6 +5,8 @@ Version 2.0.2
 
 Unreleased
 
+-  Fix type annotation for ``teardown_request``. :issue:`4093`
+
 
 Version 2.0.1
 -------------

src/flask/typing.py

@@ -37,7 +37,7 @@
 AfterRequestCallable = t.Callable[["Response"], "Response"]
 BeforeRequestCallable = t.Callable[[], None]
 ErrorHandlerCallable = t.Callable[[Exception], ResponseReturnValue]
-TeardownCallable = t.Callable[[t.Optional[BaseException]], "Response"]
+TeardownCallable = t.Callable[[t.Optional[BaseException]], None]
 TemplateContextProcessorCallable = t.Callable[[], t.Dict[str, t.Any]]
 TemplateFilterCallable = t.Callable[[t.Any], str]
 TemplateGlobalCallable = t.Callable[[], t.Any]