Jobs: a vouch is no longer cleared by secrets scoped to other sandboxes by ID

Any change to an egress secret's scope, including a list of other sandboxes' IDs, cleared every vouch in the organization, and the job's runs carried no job_vouched_by claim in their identity tokens. Scopes by sandbox ID no longer affect a vouch, except for a run whose own sandbox ID is added to one, which carries no job_vouched_by claim. A change to a secret with no scope, a label or App scope, a secret's policy, or the upstream proxy still clears the vouch until an owner or admin vouches again. Vouches that were in effect when this change was released remain in effect.