Center platform options vertically

What does this MR do and why?

Center platform options vertically

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the feature: Feature.enable(:create_runner_workflow_for_admin) in rails c.
2. Visit Admin > Runners
3. Select New instance runner to visit then /new page (example URL http://gdk.test:3000/admin/runners/new)

MR 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 MR.

Related to #390423