Remove experimental.NoReturn (#7475)

python/ray/experimental/no_return.py

@@ -1,11 +0,0 @@
-class NoReturn:
-    """Do not store the return value in the object store.
-
-    If a task returns this object, then Ray will not store this object in the
-    object store. Calling `ray.get` on the task's return ObjectIDs may block
-    indefinitely unless the task manually stores an object for the
-    corresponding ObjectID.
-    """
-
-    def __init__(self):
-        raise TypeError("The `NoReturn` object should not be instantiated")