Use primary variant for new release button

What does this MR do and why?

This MR migrates the New release button on the releases overview page to the correct primary variant.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Go to a project where you have at least developer access
2. Go to Deployments > Releases
3. See the New release button

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.