fix(theme-classic): fix docs layout issue

[slorber]

Motivation

Little layout bug reported here, only affecting v2.x (already fixed in 3.x but not backportable)

#8369 (comment)

Test Plan

preview

Test links

https://deploy-preview-8707--docusaurus-2.netlify.app/tests/docs/more-test

Related issues/PRs

#8369

[netlify]

✅ [V2]

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🔨 Latest commit	1d8e8e1
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😎 Deploy Preview	https://deploy-preview-8707--docusaurus-2.netlify.app
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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 89	🟢 100	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 78	🟢 100	🟢 100	🟢 100	🟢 90	Report

[github-actions]

Size Change: +23 B (0%)

Total Size: 814 kB

ℹ️ View Unchanged

Filename	Size	Change
website/.docusaurus/globalData.json	53.5 kB	0 B
website/build/assets/css/styles.********.css	106 kB	+23 B (0%)
website/build/assets/js/main.********.js	615 kB	0 B
website/build/index.html	39.1 kB	0 B

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