Fix readthedocs config file

Author: olofk

.readthedocs.yml

@@ -11,13 +11,15 @@ formats: all
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-  version: 3.8
   install:
     - requirements: doc/requirements.txt
     - method: pip
       path: .
 
 build:
+  os: "ubuntu-22.04"
+  tools:
+    python: "3.11"
   jobs:
     post_checkout:
       - git fetch --unshallow  || true