Clamp docutils to 0.20.x until we're done with 3.8

setup.py

@@ -35,6 +35,9 @@ def version():
             # https://black.readthedocs.io/en/stable/the_black_code_style/index.html#stability-policy
             'black>=24.3.0,<25.0.0',
             'build>=0.7.0',
+            # docutils 0.21.x bumped to >=3.9 and 3.8 is still active. we'll
+            # have to clamp it down until we remove 3.8
+            'docutils<=0.20.1',
             'isort>=5.11.5',
             'pyflakes>=2.2.0',
             'readme_renderer[md]>=26.0',