[packaging] Remove a sphinx only reference from the Readme

This link is also used in the metadata and the Github's readme

It needs to be pure RST

Author: Pierre-Sassoulas

README.rst

@@ -69,8 +69,9 @@ ecosystem of existing plugins for popular frameworks and third party libraries.
     to start is ``PyPI`` which often returns a plugin by searching for
     ``pylint <library>``. `pylint-pydantic`_, `pylint-django`_ and
     `pylint-sonarjson`_ are examples of such plugins. More information about plugins
-    and how to load them can be found at :ref:`plugins <plugins>`.
+    and how to load them can be found at `plugins`_.
 
+.. _`plugins`: https://pylint.pycqa.org/en/latest/development_guide/how_tos/plugins.html#plugins
 .. _`pylint-pydantic`: https://pypi.org/project/pylint-pydantic
 .. _`pylint-django`: https://github.com/PyCQA/pylint-django
 .. _`pylint-sonarjson`: https://github.com/omegacen/pylint-sonarjson