Improve layout and text of "too many changes" alert

What does this MR do and why?

• Updates text of "too many changes" alert
• Increases spacing
• Use secondary button type for both actions
• Uses Patches instead of Email patches for action button (related to !115989 (merged))

Screenshots or screen recordings

Before	After

How to set up and validate locally

Go to a merge request with a large number of changes (example I used is from !1 in gitlab-shell)

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.

#394879 (closed)