Merge pull request #2899 from freifunk-gluon/readthedocs-yaml

readthedocs: specify build-container

.readthedocs.yml

@@ -11,6 +11,10 @@ sphinx:
 
 # Optionally set the version of Python and requirements required to build your docs
 python:
-   version: 3.8
    install:
    - requirements: docs/requirements.txt
+
+build:
+    os: ubuntu-22.04
+    tools:
+        python: "3.8"