Avoid error from Sphinx 4.3.0 (#831)

bhrutledge · web-flow · commit c9c21a78d615 · 2021-11-12T07:07:03.000-05:00
diff --git a/docs/requirements.txt b/docs/requirements.txt
@@ -1,5 +1,5 @@
 doc8>=0.8.0
 furo>=2021.10.09
 readme-renderer>=17.4
-Sphinx>=4.2.0
+Sphinx>=4.2.0,<4.3  # https://github.com/sphinx-doc/sphinx/issues/9844
 sphinxcontrib-programoutput>=0.17
