fix: growth of content container to take all the available space

[dawei-wang]

Fixes #8369
Issue fix: To prevent content container growth, to take all the available space.

Pre-flight checklist

• [v ] I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Test Plan

Test links

https://deploy-preview-8442--docusaurus-2.netlify.app/
https://deploy-preview-8442--docusaurus-2.netlify.app/tests/docs/doc-with-another-sidebar

Related issues/PRs

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 83	🟢 97	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟠 77	🟢 100	🟢 100	🟢 100	🟢 90	Report

[Josh-Cena]

@dawei-wang Normally I won't be reviewing CSS changes, but just want to drop by and say hi—nice seeing you here as well 😄

[slorber]

Unfortunately, we don't want to un-necessarily push the footer outside the full viewport height 😅

I want to see the full footer in the viewport here, and not having to scroll to see it.

https://deploy-preview-8442--docusaurus-2.netlify.app/tests/docs/doc-with-another-sidebar

[slorber]

Closing in favor of #8463