demos: allow running without `ui.allow-init-native = true`
We need to use the native backend here because of but we
shouldn't require the user running the script to have it in their
config.
@@ -3,7 +3,7 @@ set -euo pipefail
. "$(dirname "$0")"/demo_helpers.sh
new_tmp_dir
-jj init
+jj init --config-toml ui.allow-init-native=true
echo "first" > file
jj branch create first
jj commit -m 'first'
