Improve many __(a)exit__ annotations (#9696)

stubs/humanfriendly/humanfriendly/testing.pyi

@@ -65,7 +65,7 @@ class MockedProgram(CustomSearchPath):
     program_signal_file: Any
     def __init__(self, name, returncode: int = ..., script: Incomplete | None = ...) -> None: ...
     def __enter__(self): ...
-    def __exit__(self, *args, **kw): ...
+    def __exit__(self, *args: object, **kw: object): ...
 
 class CaptureOutput(ContextManager):
     stdin: Any