Refer uu users to built-in alternative in codecs module

The uu module was deprecated in Python 3.11 and removed in Python 3.13, but uuencode/uudecode functionality is still available in the standard library by using the "uu" codec with codecs.encode and codecs.decode.

Mention this in the remains of the "uu" module documentation.

Author: RavuAlHemio

Doc/library/uu.rst

@@ -13,3 +13,6 @@ being deprecated in Python 3.11.  The removal was decided in :pep:`594`.
 
 The last version of Python that provided the :mod:`!uu` module was
 `Python 3.12 <https://docs.python.org/3.12/library/uu.html>`_.
+
+Encoding and decoding can instead be achieved using :func:`codecs.encode`
+and :func:`codecs.decode`, specifying `"uu"` as the codec.