Update use of the old DNS role throughout our Terraform

[alexwlchan]

We have a bunch of Terraform stacks that refer to DNS records in the old account, with role arn:aws:iam::250790015188:role/wellcomecollection-assume_role_hosted_zone_update

We should update them to use the new role ID arn:aws:iam::267269328833:role/wellcomecollection-assume_role_hosted_zone_update

Follows #4561

[alexwlchan]

This search highlights uses of the old role: https://github.com/search?type=Code&q=arn%3Aaws%3Aiam%3A%3A250790015188%3Arole%2Fwellcomecollection-assume_role_hosted_zone_update

[alexwlchan]

Also places where we hard-coded the old Zone ID: https://github.com/search?type=Code&q=Z3THRVQ5VDYDMC

[alexwlchan]

Done.