Link to the devguide's PR guidelines (GH-932)

.github/CONTRIBUTING.rst

@@ -29,10 +29,8 @@ everything from how to build the code to submitting a pull request. There are
 also suggestions on how you can most effectively help the project.
 
 Please be aware that our workflow does deviate slightly from the typical GitHub
-project. Issues are tracked at https://bugs.python.org/ and should be mentioned
-in pull requests using the format of ``bpo-12345`` . If your pull request is in
-response to a specific issue then please mention it in the title,
-e.g. “bpo-12345: fix comment in tokenizer.c”.
+project. Details on how to properly submit a pull request are covered in
+`Lifecycle of a Pull Request <https://cpython-devguide.readthedocs.io/pullrequest.html>`_.
 
 If you are making a code contribution or large documentation contribution,
 please feel free to add yourself to the ``Misc/ACKS`` file alphabetically.