Readthedocs requires specific distro version

Change-Id: I5530d5c29145727abfbfe8c651784d39506d053d
Signed-off-by: czichy <thoralf.czichy@nokia.com>
diff --git a/.readthedocs.yaml b/.readthedocs.yaml
index 243587e..69608f4 100644
--- a/.readthedocs.yaml
+++ b/.readthedocs.yaml
@@ -9,7 +9,7 @@
   - htmlzip
 
 build:
-  os: latest
+  os: "ubuntu-22.04"
   tools:
     python: "3.7"