Change button variant to confirm of empty branch MR

What does this MR do and why?

Fix the button variant

Screenshots or screen recordings

As-is	To-be

How to set up and validate locally

1. Create an empty branch in any project on the GDK
2. Create an empty merge request from the branch
3. Go to the Changes tab

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.