Re-run create-kustomization-variables-configmaps-script on change

We have a migration script for creating per-app kustomization variables at cluster creation, which as of now only sets the default app subdomains if they're not already manually set to something else.

When we added Hedgedoc just now, we added to that script, but for existing clusters the script is not run again, so the app kustomization variables remain unset and the hedgedoc kustomization fails when Hedgedoc is installed.

We may try to re-run the script by changing a property of the kubernetes Job that is immutable, and set spec.force: true on the migration kustomization. If I understand correctly then flux should delete and recreate the Job, and it will be run again. Note that apart from the addition of Hedgedoc, the script is idempotent so it's okay to run it again on an existing cluster.