The ghp agent role fails at apply with `installation_id is required for
agent tokens` because config/ghp_secret_backend_role/ghp/agent.yaml carries a
placeholder installation_id. Remove the role for now so the master apply goes
green and does not block the arrstack #127 apply. The ghp backend is retained;
re-add the role once a real installation_id is available.
- Delete config/ghp_secret_backend_role/ghp/agent.yaml (empties the
ghp_secret_backend_role for_each map).