functools: Add partial.__new__; remove partial.__init__ (#6813)

Author: NeilGirdhar

stdlib/functools.pyi

@@ -51,7 +51,7 @@ class partial(Generic[_T]):
     func: Callable[..., _T]
     args: tuple[Any, ...]
     keywords: dict[str, Any]
-    def __init__(self, func: Callable[..., _T], *args: Any, **kwargs: Any) -> None: ...
+    def __new__(cls: Type[_S], __func: Callable[..., _T], *args: Any, **kwargs: Any) -> _S: ...
     def __call__(self, *args: Any, **kwargs: Any) -> _T: ...
     if sys.version_info >= (3, 9):
         def __class_getitem__(cls, item: Any) -> GenericAlias: ...