fix: CSS class had single quote in name

[nschonni]

Why:

The CSS class was incorrect because of a stray single quote character

What's being changed:

Remove single quote to make the class border-top instead of bord'er-top

Check off the following:

• All of the tests are passing.
• I have reviewed my changes in staging.
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[janiceilene]

Thanks @nschonni! I'll get this triaged for review 💖

[github-actions]

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