Fix the ReadTheDocs config (#1091)

Fixes "Config validation error in build.os. Value build not found."

Author: meooow25

.readthedocs.yml

@@ -1,11 +1,15 @@
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
 version: 2
 
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.7"
+
 sphinx:
   configuration: containers/docs/conf.py
 
 submodules:
   include:
     - containers/docs/_extensions/haddock-autolink
-
-python:
-  version: 3.7