Add a label to pganssle's post link on deprecating setup.py

I noticed it as it ended up in the translation strings.

Author: webknjaz

source/discussions/setup-py-deprecated.rst

@@ -210,6 +210,6 @@ has now been reduced to the role of a build backend.
 Where to read more about this?
 ==============================
 
-* https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html
+* `Why you shouldn't invoke setup.py directly by Paul Ganssle <https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html>`__
 
 * :doc:`setuptools:deprecated/commands`