.readthedocs.yaml: use dependency groups; bump OS.

Author: lemon24

.readthedocs.yaml

@@ -1,16 +1,13 @@
 version: 2
 
 build:
-  os: ubuntu-22.04
+  os: ubuntu-24.04
   tools:
     python: "3"  # (last stable CPython version)
 
 python:
   install:
-    - method: pip
-      path: .
-      extra_requirements:
-        - docs
+    - pip install --group docs
 
 sphinx:
     configuration: docs/conf.py