scripts: update hetzner amd64 instance type

[apricote]

scripts: update hetzner amd64 instance type

The currently used server type (cpx11) was deprecated and will be removed on 2026-01-01.

• https://www.hetzner.com/news/new-cloud-plans/
• https://docs.hetzner.cloud/changelog#2025-10-16-new-server-types-with-categories
• https://docs.hetzner.cloud/changelog#2025-10-16-server-types-deprecated

How to use

Run Hetzner tests in Jenkins

Testing done

None, I just replaced the server type used for Hetzner tests.

• [ ] Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• [ ] Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.