gh-129169: update `asyncio.ensure_future` docs to suggest taskgroups

Co-authored-by: Kumar Aditya <kumaraditya@python.org>

Doc/library/asyncio-future.rst

@@ -51,12 +51,13 @@ Future Functions
 
    .. important::
 
-      See also the :func:`create_task` function which is the
-      preferred way for creating new Tasks.
-
       Save a reference to the result of this function, to avoid
       a task disappearing mid-execution.
 
+      See also the :func:`create_task` function which is the
+      preferred way for creating new tasks or use :class:`asyncio.TaskGroup`
+      which keeps reference to the task internally.
+
    .. versionchanged:: 3.5.1
       The function accepts any :term:`awaitable` object.