Different reqs

docs/requirements.txt

@@ -2,5 +2,6 @@ cython>=0.20
 numpy>=1.9
 
 # Note: beware of https://github.com/readthedocs/sphinx_rtd_theme/issues/1115
-sphinx
+docutils==0.17.1
+sphinx>=4.3.0
 sphinx-rtd-theme>=1.0.0