Restrict docutils version to fix documenation CI (#1100)

* Installed `sphinx` in the CI needs `docutils<0.20`

setup.py

@@ -127,6 +127,7 @@ def run(self, *args, **kwargs):
         "sphinxcontrib-htmlhelp<=2.0.0", # After this version it needs a toml file to work, no more setup.py
         "sphinx<6",
         "sphinx-rtd-theme", # needs sphinx < 7
+        "docutils<0.20", # needed by sphinx
     ]
     + install_requirements,
     install_requires=install_requirements,