Use danger button variant in comment delete modal

What does this MR do and why?

For the Delete Comment modal:

• Uses danger variant for modal button
• Updates modal button text

#344156 (closed) (for epic &6854 (closed))

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable feature flag Feature.enable(:bootstrap_confirmation_modals)
2. Navigate to a Git commit for any project.
3. Create a comment.
4. Click the vertical dotdotdot menu and click "delete comment"
5. Observe. The modal should appear.

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 #344156 (closed)