Fix code line highlighting

[johnnymetz]

What does this PR change? What problem does it solve?

Fix code line highlighting by deleting a CSS rule.

Verified this works locally and looks good (see the images in the related discussion).

Was the change discussed in an issue or in the Discussions before?

#525

PR Checklist

• This change adds/updates translations and I have used the template present here.
• I have enabled maintainer edits for this PR.
• I have verified that the code works as described/as intended.
• This change adds a Social Icon which has a permissive license to use it.
• This change does not include any CDN resources/links.
• This change does not include any unrelated scripts such as bash and python scripts.
• This change updates the overridden internal templates from HUGO's repository.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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[adityatelange]

Approving for now, but don't remember where this was needed for hljs to work, Thanks!