stdlib: audit more callback annotations (#8209)

stdlib/_thread.pyi

@@ -19,7 +19,7 @@ class LockType:
         self, type: type[BaseException] | None, value: BaseException | None, traceback: TracebackType | None
     ) -> None: ...
 
-def start_new_thread(function: Callable[..., Any], args: tuple[Any, ...], kwargs: dict[str, Any] = ...) -> int: ...
+def start_new_thread(function: Callable[..., object], args: tuple[Any, ...], kwargs: dict[str, Any] = ...) -> int: ...
 def interrupt_main() -> None: ...
 def exit() -> NoReturn: ...
 def allocate_lock() -> LockType: ...