fix progress and cancel callback typing

Author: T4rk1n

dash/_callback.py

@@ -68,10 +68,10 @@ def callback(
     *_args,
     background: bool = False,
     interval: int = 1000,
-    progress: Optional[Output] = None,
+    progress: Optional[Union[List[Output], Output]] = None,
     progress_default: Any = None,
     running: Optional[List[Tuple[Output, Any, Any]]] = None,
-    cancel: Optional[List[Input]] = None,
+    cancel: Optional[Union[List[Input], Input]] = None,
     manager: Optional[BaseBackgroundCallbackManager] = None,
     cache_args_to_ignore: Optional[list] = None,
     on_error: Optional[Callable[[Exception], Any]] = None,