Update alert.mdx

[nickalbrecht]

Correction for a element

Description

Fix for what I believe is a typo, in the documentation for an example usage of the Alert component

Motivation & Context

Bug fix

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

[julien-deramond]

Thanks @nickalbrecht! Indeed <vstack> isn’t an element Bootstrap styles, so <div class="vstack"> is the right fix. The cheatsheet’s alert example had the same typo, so I pushed a commit to fix it too. Since .vstack is a flex column, the margins around the <hr> no longer merge with the paragraph’s, which added extra space above the line. A second commit adds .mt-0 on the <hr> in both examples, so they look exactly as before. LGTM