Apply suggestions from code review

Co-authored-by: Sebastian Rittau <sebastian.rittau@zfutura.de>

Author: donbarbos

stubs/boltons/boltons/funcutils.pyi

@@ -1,5 +1,5 @@
 import functools
-from _typeshed import Incomplete
+from _typeshed import Incomplete, Unused
 from collections.abc import Callable
 from functools import total_ordering as total_ordering
 from typing import TypeVar
@@ -64,5 +64,5 @@ class FunctionBuilder:
 class MissingArgument(ValueError): ...
 class ExistingArgument(ValueError): ...
 
-def noop(*args, **kwargs) -> None: ...
+def noop(*args: Unused, **kwargs: Unused) -> None: ...
 def once(func: Callable[[], _R]) -> Callable[[], _R]: ...