Use Ruby 3.0 compatible syntax for endless methods

What does this MR do and why?

Fix https://gitlab.com/gitlab-org/gitlab/-/pipelines/1148394801

Brought up at !141642 (comment 1738503656)

Also fix https://gitlab.com/gitlab-org/gitlab/-/jobs/5993165683 which was broken by !142156 (merged)

How to validate

• rails-production-server-boot-puma-example for this merge request under pipeline:run-in-ruby3_0: https://gitlab.com/gitlab-org/gitlab/-/jobs/5993165592
• rails-production-server-boot-puma-example for ruby30: https://gitlab.com/gitlab-org/gitlab/-/jobs/5992753687