Make Ruby 3.0.5 the only ruby for the project

What does this MR do and why?

To contribute to: #1375 (closed), make Ruby 3.0.5 the only version of Ruby in the project.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.
2. Check out branch.
3. Local tasks work as expected.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.