Avoid sphinx 6.x for now

cderici · cderici · commit 2522cdf33268 · 2023-07-14T10:52:33.000-06:00
As it turns out that the sphinx &gt;=6.x doesn't play well with
coroutines.
diff --git a/docs/requirements.txt b/docs/requirements.txt
@@ -1,6 +1,6 @@
 pytz
 pymacaroons
-sphinx==4.3.2
+sphinx==5.3.0
 sphinxcontrib-asyncio
 sphinx_rtd_theme
 websockets
