Add RAPIDS Support Notice to README/docs

Author: pentschev

README.md

@@ -1,5 +1,5 @@
 > [!CAUTION]
-> UCX-Py has been discontinued, version 0.45 (RAPIDS 25.08) was its last release and it will receive no further updates. Projects depending on UCX-Py are advised to migrate to [UCXX](https://github.com/rapidsai/ucxx) immediately. [UCXX documentation](https://docs.rapids.ai/api/ucxx/nightly/).
+> UCX-Py has been discontinued, version 0.45 (RAPIDS 25.08) was its last release and it will receive no further updates, see the [RAPIDS Support Notice 50](https://docs.rapids.ai/notices/rsn0050/) for details. Projects depending on UCX-Py are advised to migrate to [UCXX](https://github.com/rapidsai/ucxx) immediately. [UCXX documentation](https://docs.rapids.ai/api/ucxx/nightly/).
 
 [![https://ucx-py.readthedocs.io/en/latest/](https://readthedocs.org/projects/ucx-py/badge/ "ReadTheDocs")]( https://ucx-py.readthedocs.io/en/latest/ )
 

docs/source/index.rst

@@ -3,7 +3,7 @@ UCX-Py
 
 .. warning::
 
-    UCX-Py has been discontinued, version 0.45 (RAPIDS 25.08) was its last release and it will receive no further updates. Projects depending on UCX-Py are advised to migrate to `UCXX <https://github.com/rapidsai/ucxx>`_ immediately. `UCXX documentation <https://docs.rapids.ai/api/ucxx/nightly/>`_.
+    UCX-Py has been discontinued, version 0.45 (RAPIDS 25.08) was its last release and it will receive no further updates, see the `RAPIDS Support Notice 50 <https://docs.rapids.ai/notices/rsn0050/>`_ for details. Projects depending on UCX-Py are advised to migrate to `UCXX <https://github.com/rapidsai/ucxx>`_ immediately. `UCXX documentation <https://docs.rapids.ai/api/ucxx/nightly/>`_.
 
 UCX-Py is the Python interface for `UCX <https://github.com/openucx/ucx>`_, a low-level high-performance networking library.  UCX and UCX-Py supports several transport methods including InfiniBand and NVLink while still using traditional networking protocols like TCP.