gh-142044: Move timeout preference to class description

Move the guidance about preferring asyncio.timeout()/timeout_at()
from a .. note:: block into the Timeout class description text,
per reviewer feedback.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kovan

Doc/library/asyncio-task.rst

@@ -766,16 +766,14 @@ Timeouts
     The context manager produced by :func:`asyncio.timeout` can be
     rescheduled to a different deadline and inspected.
 
-    .. note::
-
-       Prefer using :func:`asyncio.timeout` or :func:`asyncio.timeout_at`
-       rather than instantiating :class:`Timeout` directly.
-
     .. class:: Timeout(when)
 
        An :ref:`asynchronous context manager <async-context-managers>`
        for cancelling overdue coroutines.
 
+       Prefer using :func:`asyncio.timeout` or :func:`asyncio.timeout_at`
+       rather than instantiating :class:`Timeout` directly.
+
        ``when`` should be an absolute time at which the context should time out,
        as measured by the event loop's clock: