[arch-dev-public] Removing Ionuț as a master key holder

Ionut has done no signing/revoking for six months now. When queried on IRC, he has repeatedly stated that it will be dealt with tomorrow. This is not a great issue currently as people require three valid signatures from the five master keyholders, so adding/remove devs/TUs is working fine. But it is time to consider rotating in a new master key holder. Allan