Tweak column widths on two factor warning messages

What does this MR do?

Resolves the issue reported at https://gitlab.com/gitlab-org/gitlab-ce/issues/37546

Are there points in the code the reviewer needs to double check?

It wasn't an issue with margin as guessed in the issue, but the text of the button forcing it wider than the column. I increased the column width for the button and made it a block so the gutter wouldn't be too wide.

Screenshots (if relevant)

Before:

After:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/37546