Upgraded readthedocs recipe

Refs #691 (comment)

Author: simonw

.readthedocs.yaml

@@ -4,16 +4,13 @@ sphinx:
   configuration: docs/conf.py
 
 build:
-  os: ubuntu-22.04
+  os: ubuntu-24.04
   tools:
-    python: "3.11"
-
-python:
-  install:
-  - method: pip
-    path: .
-    dependency-groups:
-    - dev
+    python: "3.13"
+  jobs:
+    install:
+    - pip install --upgrade pip
+    - pip install --group 'docs'
 
 formats:
 - pdf