Fix return type annotation of Map.__reduce__

Author: hukkinj1

immutables/_map.pyi

@@ -43,7 +43,7 @@ class Map(Mapping[K, V]):
     def __init__(
         self, col: Union[Mapping[K, V], Iterable[Tuple[K, V]]] = ..., **kw: V
     ): ...
-    def __reduce__(self) -> NoReturn: ...
+    def __reduce__(self) -> Tuple[Type[Map], Tuple[dict]]: ...
     def __len__(self) -> int: ...
     def __eq__(self, other: Any) -> bool: ...
     def update(