ci: T8943: sweep HIGH-producer pins to renamed branches (rollout 1c) (#477)
Rewrites uses: pins to the three HIGH-fanout producers (vyos/.github,
vyos/vyos-cla-signatures, VyOS-Networks/vyos-reusable-workflows) from their
old default branch to the new production compat branch staged in Task 1.
No functional change; pin-ref rewrite only.
Tracking: T8943