build_docs.yml edited, running in container

Author: hherlyng

.github/workflows/build_docs.yml

@@ -17,7 +17,7 @@ defaults:
 jobs:
   build-book:
     runs-on: ubuntu-latest
-
+    container: ubuntu:22.04
     env:
       PYVISTA_OFF_SCREEN: false
       PYVISTA_JUPYTER_BACKEND: "panel"