fix: unexpected shift of the entire article when anchor hidden = false

[jabee0228]

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

When a heading occupies an entire line, moving the mouse over the heading causes the entire article to unexpectedly shift down by one line.
And adjusted the anchor's underline to align with this modification.

Before:

After the fix, the following effects are achieved:

Line breaks will also be correct:

h1, h2, h3, h4, h5, and h6 all function correctly.

Was the change discussed in an issue or in the Discussions before?
No, this bug was found when I was writing an article.

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.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud