Use TypeIs in is_dataclass (#11929)

stdlib/dataclasses.pyi

@@ -5,7 +5,7 @@ from _typeshed import DataclassInstance
 from builtins import type as Type  # alias to avoid name clashes with fields named "type"
 from collections.abc import Callable, Iterable, Mapping
 from typing import Any, Generic, Literal, Protocol, TypeVar, overload
-from typing_extensions import TypeAlias, TypeGuard
+from typing_extensions import TypeAlias, TypeIs
 
 if sys.version_info >= (3, 9):
     from types import GenericAlias
@@ -214,11 +214,9 @@ else:
 
 def fields(class_or_instance: DataclassInstance | type[DataclassInstance]) -> tuple[Field[Any], ...]: ...
 @overload
-def is_dataclass(obj: DataclassInstance) -> Literal[True]: ...
+def is_dataclass(obj: type) -> TypeIs[type[DataclassInstance]]: ...
 @overload
-def is_dataclass(obj: type) -> TypeGuard[type[DataclassInstance]]: ...
-@overload
-def is_dataclass(obj: object) -> TypeGuard[DataclassInstance | type[DataclassInstance]]: ...
+def is_dataclass(obj: object) -> TypeIs[DataclassInstance | type[DataclassInstance]]: ...
 
 class FrozenInstanceError(AttributeError): ...