Fix doc build warning

This fixes the following doc build warning:
```
Warning, treated as error:
Failed to read intersphinx_mapping[https://docs.python.org/3/], ignored: SphinxWarning('The pre-Sphinx 1.0 \'intersphinx_mapping\' format is deprecated and will be removed in Sphinx 8. Update to the current format as described in the documentation. Hint: "intersphinx_mapping = {\'<name>\': (\'https://docs.python.org/3/\', \'python-intersphinx.inv\')}".https://www.sphinx-doc.org/en/master/usage/extensions/intersphinx.html#confval-intersphinx_mapping')
```

docs/conf.py

@@ -81,4 +81,4 @@
 htmlhelp_basename = 'Freshmakerdoc'
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'https://docs.python.org/3/': 'python-intersphinx.inv'}
+intersphinx_mapping = {'python': ('https://docs.python.org/3/', 'python-intersphinx.inv')}