Update readthedocs config to use dependency groups

Author: RalfG

.readthedocs.yml

@@ -4,14 +4,11 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.11"
+  jobs:
+    install:
+      - pip install --upgrade pip
+      - pip install --group 'docs' .
 
 sphinx:
   configuration: docs/source/conf.py
   builder: dirhtml
-
-python:
-  install:
-    - method: pip
-      path: .
-      extra_requirements:
-        - docs