Change button variant to confirm in the requirement drawer

What does this MR do and why?

Fix the button variant success -> confirm

Screenshots or screen recordings

As-is	To-be

How to set up and validate locally

1. Go to any of the projects you have owner access to on the GDK (I used gitlab-shell)
2. Go to Issues > Requirements
3. Create one requirement and check the drawer on the right side.

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.