Remove the AR EC2 app and related resources in AWS. Some or most of this may be achievable by modifying CDK. Confirmed with DevX that the AR stack needs to be deleted manually.

• Remove continuous and scheduled deployments for Mobile::mobile-apps-rendering in Riff-Raff
• Manually delete CloudFormation stacks in AWS (DevX suggest pairing on this to ensure the correct stacks are deleted!)
• Open a PR to remove AR CDK code and ar-ci workflow
• Remove ar-ci from repo's branch protection rules and merge PR