Temporarily pin Fedora version to 40 until I transition to 41 properly

- Sleep Through Notifications extension is not ported to Gnome 47 (but changing metadata.json works)
- Wanting to get rid of inferior `tuned` & to retain `power-profiles-daemon`

recipes/recipe.yml

@@ -5,7 +5,7 @@ description: My personalized custom OS image.
 
 # the base image to build on top of (FROM) and the version tag to use
 base-image: ghcr.io/ublue-os/silverblue-main
-image-version: latest # latest is also supported if you want new updates ASAP
+image-version: 40 # latest is also supported if you want new updates ASAP
 
 # module configuration, executed in order
 # you can include multiple instances of the same module