Build docs with Python 3.13

Author: cgoldberg

py/docs/.readthedocs.yaml

@@ -10,7 +10,7 @@ version: 2
 build:
   os: ubuntu-24.04
   tools:
-    python: "latest"
+    python: "3.11"
   commands:
     - pip install -r py/docs/requirements.txt
     - pip install -r py/requirements.txt