prune-dist.yml: run in cockpit-dist upload
prune-dist.yml: run in cockpit-dist upload

Run in the cockpit-dist upload environment and access the repository
via ssh with the deploy key instead of https via COCKPITUOUS_TOKEN.

Add restricted permissions: for good measure.

cockpit-project/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,mvollmer/cockpit,cockpit-project/cockpit