Comply with new readthedocs requirements

.readthedocs.yml

@@ -5,6 +5,11 @@
 # Required
 version: 2
 
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
 # Build documentation in the doc/ directory with Sphinx
 sphinx:
   configuration: doc/conf.py
@@ -14,7 +19,7 @@ formats: all
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-  version: 3.8
+  version: 3.11
   install:
     - requirements: doc/requirements.txt
     - method: pip