bpo-30737: Update DevGuide links to new URL (GH-3228)

Update old devguide links from https://docs.python.org/devguide to https://devguide.python.org
diff --git a/Doc/using/unix.rst b/Doc/using/unix.rst
index 604688c..8b96ebe 100644
--- a/Doc/using/unix.rst
+++ b/Doc/using/unix.rst
@@ -67,7 +67,7 @@
 If you want to compile CPython yourself, first thing you should do is get the
 `source <https://www.python.org/downloads/source/>`_. You can download either the
 latest release's source or just grab a fresh `clone
-<https://docs.python.org/devguide/setup.html#getting-the-source-code>`_.  (If you want
+<https://devguide.python.org/setup/#getting-the-source-code>`_.  (If you want
 to contribute patches, you will need a clone.)
 
 The build process consists in the usual ::
@@ -140,4 +140,4 @@
 
 Please go to `Python Editors <https://wiki.python.org/moin/PythonEditors>`_ and
 `Integrated Development Environments <https://wiki.python.org/moin/IntegratedDevelopmentEnvironments>`_
-for a comprehensive list.
\ No newline at end of file
+for a comprehensive list.