Also bump metadata CI job to Fedora 40

.gitlab/linux-metadata-validate.yml

@@ -6,7 +6,7 @@ validate_linux_metadata:
   needs: []
   interruptible: false
   # This is the only CI image with the utilities needed for this test
-  image: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:38
+  image: registry.gitlab.com/kicad/kicad-ci/source_containers/master/fedora:40
   # Due to bug https://github.com/hughsie/appstream-glib/issues/381, this doesn't think our description tag
   # is localized even though it actually is.
   allow_failure: true