Try newer version of Sphinx.

anthony-tuininga · anthony-tuininga · commit 5728cf534e24 · 2021-11-04T16:02:28.000-06:00
diff --git a/doc/requirements.txt b/doc/requirements.txt
@@ -1,2 +1,2 @@
-sphinx==3.4.3
+sphinx==4.1.2
 sphinx_rtd_theme==0.5.1
