Update ReadTheDocs settings.

.readthedocs.yaml

@@ -9,7 +9,12 @@ python:
 # OMG, and this is what they do with a cross-platform language!
 # from https://docs.readthedocs.io/en/stable/config-file/v2.html#build-os
 build:
-  os: ubuntu-22.04
+    os: ubuntu-22.04
+    tools:
+        python: "3.11"
+
+sphinx:
+    configuration: docs/source/conf.py
 
 # have to explicitly enable that,
 # https://docs.readthedocs.io/en/stable/config-file/v2.html#formats