Joined Cases T-720/19 to T-725/19: Judgment of the General Court of 15 September 2021 — Ashworth and Others v Parliament (Law governing the institutions — Rules governing the payment of expenses and allowances to Members of the Parliament — Amendment of the additional voluntary pension scheme — Notice fixing additional voluntary pension rights — Plea of illegality — Competence of the Bureau of the Parliament — Rights acquired or in the process of being acquired — Proportionality — Equal treatment — Legal certainty)