Revert envorce of Python version by noxfile.py

Author: rgaiacs

noxfile.py

@@ -5,7 +5,7 @@
 nox.options.reuse_existing_virtualenvs = True
 
 
-@nox.session(python="3.13", default=False)
+@nox.session(default=False)
 def docs(session):
     """
     Build the documentation and, optionally with '-- live', run a web server.